Xenopus laevis stage series: complete
Digitized images and developmental data from Nieuwkoop and Faber (1994) Normal Table of Xenopus laevis (Daudin).
Garland Publishing Inc, New York ISBN 0-8153-1896-0.
Click on the small images to download larger versions (most are < 0.1 MB, 300 dpi
jpg files, and TIFF files are also available).
Copyright © 1994 Pieter D. Nieuwkoop and J. Faber. Digital images created by Xenbase.
![Nieuwkoop and Faber stage 1; age 0 hr; corresponding to the following external morphological criteria: One cell stage, shortly after fertilization. Pigmentation darker ventrally than dorsally. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage01animal.jpg)
Stage 1 (egg), animal view
0 min pf @ 23°c
![Nieuwkoop and Faber stage 1; age 0 hr; corresponding to the following external morphological criteria: One cell stage, shortly after fertilization. Pigmentation darker ventrally than dorsally. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage01dorsal.jpg)
Stage 1 (egg), dorsal view
0 min pf @ 23°c
![Nieuwkoop and Faber stage 1; age 0 hr; corresponding to the following external morphological criteria: One cell stage, shortly after fertilization. Pigmentation darker ventrally than dorsally. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage01ventral.jpg)
Stage 1 (egg), ventral view
0 min pf @ 23°c
![Nieuwkoop and Faber stage 2-; age 1 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Beginning of first cleavage. First cleavage groove has not yet reached vegetal pole. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage02minusanimal.jpg)
Stage 2- (2-cell), animal view
1 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 2; age 1 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced two cell stage. First cleavage groove has reached vegetal pole. Ventral side of blastomeres darker than dorsal side. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage02animal.jpg)
Stage 2 (2-cell), animal view
1 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 2; age 1 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced two cell stage. First cleavage groove has reached vegetal pole. Ventral side of blastomeres darker than dorsal side. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage02ventral.jpg)
Stage 2 (2-cell), ventral view
1 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 3; age 2 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced four-cell stage. Second cleavage groove has reached vegetal pole. In animal view dorsal blastomeres usually smaller than ventral ones; the latter darker than the former. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage03animal.jpg)
Stage 3 (4-cell), animal view
2 hr pf @ 23°c
![Nieuwkoop and Faber stage 3; age 2 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced four-cell stage. Second cleavage groove has reached vegetal pole. In animal view dorsal blastomeres usually smaller than ventral ones; the latter darker than the former. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage03dorsolat.jpg)
Stage 3 (4-cell), dorso-lateral view
2 hr pf @ 23°c
![Nieuwkoop and Faber stage 4; age 2 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced eight cell stage. Dorsal micro- and macromeres usually smaller than ventral ones; dorsal micromeres less pigmented than ventral ones. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage04animal.jpg)
Stage 4 (8-cell), animal view
2 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 4; age 2 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced eight cell stage. Dorsal micro- and macromeres usually smaller than ventral ones; dorsal micromeres less pigmented than ventral ones. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage04dorsolat.jpg)
Stage 4 (8-cell), lateral view
2 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 5; age 2 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced sixteen cell stage. Dorsal micromeres distinctly smaller and less pigmented than ventral ones. Macromeres entirely separated by cleavage grooves. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage05animal.jpg)
Stage 5 (16-cell), animal view
2 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 5; age 2 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced sixteen cell stage. Dorsal micromeres distinctly smaller and less pigmented than ventral ones. Macromeres entirely separated by cleavage grooves. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage05dorsal.jpg)
Stage 5 (16-cell), dorsal view
2 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 6; age 3 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Advanced thirty-two cell stage. Distinction between dorsal and ventral micromeres as in preceding stage. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage06animal.jpg)
Stage 6 (32-cell), animal view
3 hr pf @ 23°c
![Nieuwkoop and Faber stage 6.5; age 3 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Morula stage. About 48 blastomeres. In animal view about 6 micromeres along meridian. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage065animal.jpg)
Stage 6.5 blastula, animal view
3 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 6.5; age 3 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Morula stage. About 48 blastomeres. In animal view about 6 micromeres along meridian. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage065dorsal.jpg)
Stage 6.5 blastula, dorsal view
3 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 6.5; age 3 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Morula stage. About 48 blastomeres. In animal view about 6 micromeres along meridian. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage065ventral.jpg)
Stage 6.5 blastula, ventral view
3 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 7, 64-cell embryo; age 4 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Large-cell blastula stage. In animal view about 10 micromeres along meridian. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage07animal.jpg)
Stage 7 blastula, animal view
4 hr pf @ 23°c
![Nieuwkoop and Faber stage 7, 64-cell embryo; age 4 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Large-cell blastula stage. In animal view about 10 micromeres along meridian. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage07dorsal.jpg)
Stage 7 blastula, dorsal view
4 hr pf @ 23°c
![Nieuwkoop and Faber stage 7, 64-cell embryo; age 4 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Large-cell blastula stage. In animal view about 10 micromeres along meridian. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage07ventral.jpg)
Stage 7 blastula, ventral view
4 hr pf @ 23°c
![Nieuwkoop and Faber stage 8, 128-cell embryo; age 5 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Medium-cell blastula stage. Surface not yet entirely smooth. Border of animal pigment cap more diffuse at dorsal than at lateral and ventral sides. Gradual transition in cell size from animal to vegetative pole. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage08animal.jpg)
Stage 8 blastula, animal view
5 hr pf @ 23°c
![Nieuwkoop and Faber stage 8, 128-cell embryo; age 5 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Medium-cell blastula stage. Surface not yet entirely smooth. Border of animal pigment cap more diffuse at dorsal than at lateral and ventral sides. Gradual transition in cell size from animal to vegetative pole. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage08dorsal.jpg)
Stage 8 blastula, dorsal view
5 hr pf @ 23°c
![Nieuwkoop and Faber stage 8, 128-cell embryo; age 5 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Medium-cell blastula stage. Surface not yet entirely smooth. Border of animal pigment cap more diffuse at dorsal than at lateral and ventral sides. Gradual transition in cell size from animal to vegetative pole. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage08ventral.jpg)
Stage 8 blastula, ventral view
5 hr pf @ 23°c
![Nieuwkoop and Faber stage 9; age 7 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Fine-cell blastula stage. Animal cells smaller at dorsal than at ventral side. Border between marginal zone and vegetative field distinct, particularly dorsally, owing to difference in cell size. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage09veg.jpg)
Stage 9 blastula, vegetal view
7 hr pf @ 23°c
![Nieuwkoop and Faber stage 10; age 9 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Initial gastrula stage. First indication of blastopore only by pigment concentration. No formation of groove. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage10veg.jpg)
Stage 10, vegetal view
9 hr pf @ 23°c
![Nieuwkoop and Faber stage 10.5; age 11 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Crescent-shaped blastopore stage. Blastopore groove angular. Vegetal field slightly decreased in size, ventral border of future yolk plug indicated by pigment contraction. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage105vega.jpg)
Stage 10.5, vegetal view
11 hr pf @ 23°c
![Nieuwkoop and Faber stage 10.5; age 11 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Crescent-shaped blastopore stage. Blastopore groove angular. Vegetal field slightly decreased in size, ventral border of future yolk plug indicated by pigment contraction. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage105vegb.jpg)
Stage 10.5, vegetal view
11 hr pf @ 23°c
![Nieuwkoop and Faber stage 11; age 11 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Horse-shoe-shaped blastopore stage. Blastopore groove surrounding about half of future yolk plug and indicated at its ventral side; future yolk plug often rounded rectangular, slightly elongated in dorso-ventral direction, diameter more than two-fifths of diameter of egg (plus or minus 50 degrees of circumference). Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage11veg.jpg)
Stage 11, vegetal view
11 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 11.5; age 12 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Large yolk plug stage. Blastopore groove closed ventrally; yolk plug not yet quite circular. At ventral side concentrated superficial pigment still visible. Diameter of yolk plug about a third of diameter of egg (plus or minus 40 degrees). Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage115veg.jpg)
Stage 11.5, vegetal view
12 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 12; age 13 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Medium yolk plug stage. Yolk plug circular; diameter somewhat less than one fourth of diameter of egg (plus or minus 25 degrees). More and less pigmented fields radiating from yolk plug. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage12veg.jpg)
Stage 12, vegetal view
13 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 12.5; age 14 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Small yolk plug stage. Future position of neural plate and median groove indicated by darker pigment lines. Yolk plug usually ovoid, variable in size. Length: 1.4 - 1.5 mm.](static/anatomy/NF/stage125postdors.jpg)
Stage 12.5, posterior-dorsal
14 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 13; age 14 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Slit-blastopore stage. Neural plate faintly delimited; slight elevation of its rostral part and slight flattening of its caudal part. Caudal part of median groove formed. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage13postdors.jpg)
Stage 13, posterior-dorsal
14 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 14; age 16 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Neural plate stage. Cerebral part of neural plate bent downwards, with median elevation at rostral end of median groove. Initial elevation of neural folds, most pronounced in future nucal region. Blastopore always slit-shaped. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage14lat.jpg)
Stage 14, lateral view
16 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 14; age 16 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Neural plate stage. Cerebral part of neural plate bent downwards, with median elevation at rostral end of median groove. Initial elevation of neural folds, most pronounced in future nucal region. Blastopore always slit-shaped. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage14postdors.jpg)
Stage 14, posterior-dorsal
16 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 15; age 17 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Early neural fold stage. Presumptive cement gland faintly circumscribed. Anterior part of neural plate roundish. Neural folds distinct, except medio-rostrally; initial formation of sharp inner ridges on neural folds in rhombencephalic region. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage15ant.jpg)
Stage 15, anterior view
17 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 15; age 17 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Early neural fold stage. Presumptive cement gland faintly circumscribed. Anterior part of neural plate roundish. Neural folds distinct, except medio-rostrally; initial formation of sharp inner ridges on neural folds in rhombencephalic region. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage15postdors.jpg)
Stage 15, posterior-dorsal
17 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 16; age 18 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Mid neural fold stage. Anterior part of neural plate rectangular; darkly pigmented eye anlagen present; neural plate sharply constricted in the middle. Inner ridges on neural folds forming angle of about 90 degrees with neural plate in rhombencephalic region. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage16ant.jpg)
Stage 16, anterior view
18 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 16; age 18 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Mid neural fold stage. Anterior part of neural plate rectangular; darkly pigmented eye anlagen present; neural plate sharply constricted in the middle. Inner ridges on neural folds forming angle of about 90 degrees with neural plate in rhombencephalic region. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage16postdors.jpg)
Stage 16, posterior-dorsal
18 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 17; age 18 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Late neural fold stage. Anterior part of neural plate oblong triangular, angles formed by eye anlagen. Neural folds approaching each other from blastopore up to anterior trunk region. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage17ant.jpg)
Stage 17, anterior view
18 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 17; age 18 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Late neural fold stage. Anterior part of neural plate oblong triangular, angles formed by eye anlagen. Neural folds approaching each other from blastopore up to anterior trunk region. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage17dorsal.jpg)
Stage 17, dorsal view
18 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 18; age 19 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Neural groove stage. Anterior part of neural plate narrow, more or less club-shaped, often narrower towards rostral end. Parallel neural folds in trunk region very close to each other, not yet touching. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage18ant.jpg)
Stage 18, anterior view
19 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 19; age 20 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Initial neural tube stage. Neural folds touching each other, except for inconstant openings at anterior and posterior end and behind nucal region. Considerable lateral extension of brain. Lateral outline of embryo still convex. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage19ant.jpg)
Stage 19, anterior view
20 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 19; age 20 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Initial neural tube stage. Neural folds touching each other, except for inconstant openings at anterior and posterior end and behind nucal region. Considerable lateral extension of brain. Lateral outline of embryo still convex. Length: 1.5 - 1.6 mm.](static/anatomy/NF/stage19dorsal.jpg)
Stage 19, dorsal view
20 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 20; age 21 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Neural folds fused, suture still present. The two eye anlagen showing through dumb-bell-shaped, eyes hardly protruding. Beginning of stretching of embryos. Lateral outline flat. Length: 1.7 - 1.8 mm.](static/anatomy/NF/stage20ant.jpg)
Stage 20, anterior view
21 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 20; age 21 hr 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Neural folds fused, suture still present. The two eye anlagen showing through dumb-bell-shaped, eyes hardly protruding. Beginning of stretching of embryos. Lateral outline flat. Length: 1.7 - 1.8 mm.](static/anatomy/NF/stage20dorsal.jpg)
Stage 20, dorsal view
21 hr 45 min pf @ 23°c
![Nieuwkoop and Faber stage 21; age 22 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Suture of neural tube completely closed. Delimitation of frontal field by pigment lines. Primary eye vesicles showing through in the form of two separate, obliquely placed oval spots; beginning of protrusion of eyes. Lateral outline of embryo just becoming concave, ventral outline flat. Length: 1.9 - 2.0 mm.](static/anatomy/NF/stage21ant.jpg)
Stage 21, anterior view
22 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 21; age 22 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Suture of neural tube completely closed. Delimitation of frontal field by pigment lines. Primary eye vesicles showing through in the form of two separate, obliquely placed oval spots; beginning of protrusion of eyes. Lateral outline of embryo just becoming concave, ventral outline flat. Length: 1.9 - 2.0 mm.](static/anatomy/NF/stage21dorsal.jpg)
Stage 21, dorsal view
22 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 22; age 24 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Distinct protrusion of eyes. Initial groove between jaw- and gill-areas only at latero-dorsal side. Lateral and ventral outlines of embryo slightly concave. Anal opening displaced to ventral side. Vitelline membrane becoming wider. Length: 2.0 - 2.2 mm.](static/anatomy/NF/stage22dorsal.jpg)
Stage 22, dorsal view
24 hr pf @ 23°c
![Nieuwkoop and Faber stage 22; age 24 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Distinct protrusion of eyes. Initial groove between jaw- and gill-areas only at latero-dorsal side. Lateral and ventral outlines of embryo slightly concave. Anal opening displaced to ventral side. Vitelline membrane becoming wider. Length: 2.0 - 2.2 mm.](static/anatomy/NF/stage22lat.jpg)
Stage 22, lateral view
24 hr pf @ 23°c
![Nieuwkoop and Faber stage 23; age 1 day, 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Jaw- and gill-areas completely separated by groove. Ventral outline of embryo more concave. Length: 2.2 - 2.4 mm.](static/anatomy/NF/stage23dorsal.jpg)
Stage 23, dorsal view
1 day, 45 min pf @ 23°c
![Nieuwkoop and Faber stage 23; age 1 day, 45 min at 22-24 Celsius; corresponding to the following external morphological criteria: Jaw- and gill-areas completely separated by groove. Ventral outline of embryo more concave. Length: 2.2 - 2.4 mm.](static/anatomy/NF/stage23lat.jpg)
Stage 23, lateral view
1 day, 45 min pf @ 23°c
![Nieuwkoop and Faber stage 24; age 1 day, 2 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Eyes protruding less far laterally than gill-area. Gill-area more prominent than jaw-area, gill-area not yet grooved. Ventral outline of embryo nicked. Tail bud discernible. Initial motor reactions to external stimulation. Length: 2.5 - 2.7 mm.](static/anatomy/NF/stage24dorsal.jpg)
Stage 24, dorsal view
1 day, 2 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 24; age 1 day, 2 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Eyes protruding less far laterally than gill-area. Gill-area more prominent than jaw-area, gill-area not yet grooved. Ventral outline of embryo nicked. Tail bud discernible. Initial motor reactions to external stimulation. Length: 2.5 - 2.7 mm.](static/anatomy/NF/stage24latsmall.jpg)
Stage 24, lateral view
1 day, 2 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 25; age 1 day, 3 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Eyes protruding equally far or further laterally than gill-area. Gill-area grooved. Invagination of otic vesicle indicated by pigment spot. Beginning of fin formation. Length: 2.8 - 3.0 mm.](static/anatomy/NF/stage25dorsal.jpg)
Stage 25, dorsal view
1 day, 3 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 25; age 1 day, 3 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Eyes protruding equally far or further laterally than gill-area. Gill-area grooved. Invagination of otic vesicle indicated by pigment spot. Beginning of fin formation. Length: 2.8 - 3.0 mm.](static/anatomy/NF/stage25lat.jpg)
Stage 25, lateral view
1 day, 3 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 26; age 1 day, 5 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: otic vesicle protruding. Pronephros distinctly visible. Myotomes showing through for the first time. Fin somewhat broadened at dorso-caudal end of body. Beginning of spontaneous movements. Length: 3.0 - 3.3 mm.](static/anatomy/NF/stage26dorsal.jpg)
Stage 26, dorsal view
1 day, 5 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 26; age 1 day, 5 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: otic vesicle protruding. Pronephros distinctly visible. Myotomes showing through for the first time. Fin somewhat broadened at dorso-caudal end of body. Beginning of spontaneous movements. Length: 3.0 - 3.3 mm.](static/anatomy/NF/stage26lat.jpg)
Stage 26, lateral view
1 day, 5 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 27; age 1 day, 7 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Lateral flattening of eyes. Fin transluscent, except for region behind anus. Tail bud formation accentuated in lateral outline. Length: 3.4 - 3.7 mm.](static/anatomy/NF/stage27dorsal.jpg)
Stage 27, dorsal view
1 day, 7 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 27; age 1 day, 7 hr 15 min at 22-24 Celsius; corresponding to the following external morphological criteria: Lateral flattening of eyes. Fin transluscent, except for region behind anus. Tail bud formation accentuated in lateral outline. Length: 3.4 - 3.7 mm.](static/anatomy/NF/stage27lat.jpg)
Stage 27, lateral view
1 day, 7 hr 15 min pf @ 23°c
![Nieuwkoop and Faber stage 28; age 1 day, 8 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Fin extending up to anus. Fin broadened and distinctly divided into outer transparent and inner translucent band. Length: 3.8 - 4.0 mm.](static/anatomy/NF/stage28dorsal.jpg)
Stage 28, dorsal view
1 day, 8 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 28; age 1 day, 8 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Fin extending up to anus. Fin broadened and distinctly divided into outer transparent and inner translucent band. Length: 3.8 - 4.0 mm.](static/anatomy/NF/stage28lat.jpg)
Stage 28, lateral view
1 day, 8 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 29 and 30; age 1 day, 11 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Gray eye cup showing through for the first time. Fin transparent up to the base over its whole length. Tail bud distinct. Length: 4.0 - 4.5 mm.](static/anatomy/NF/stage29-30lat.jpg)
Stage 29-30, lateral view
1 day, 11 hr pf @ 23°c
![Nieuwkoop and Faber stage 31; age 1 day, 13 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Tail bud equally long as broad. Length: 4.2 - 4.8 mm.](static/anatomy/NF/stage31lat.jpg)
Stage 31, lateral view
1 day, 13 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 32; age 1 day, 16 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Eye cup horse-shoe-shaped, standing out distinctly. Length of tail bud about 1.5 times its breadth. Length: 4.5 - 5.1 mm.](static/anatomy/NF/stage32lat.jpg)
Stage 32, lateral view
1 day, 16 hr pf @ 23°c
![Nieuwkoop and Faber stage 33 and 34; age 1 day, 20 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Stomodeal invagination a shallow vertical groove. Dorsal part of eye more pigmented than ventral part; distinct melanophores in dorsal part. Melanophores appearing dorsally on the head and laterally in a row extending from just below the pronephros backwards. Length of tail bud about twice its breadth. Beginning of heart beat. Length: 4.7 - 5.3 mm.](static/anatomy/NF/stage33-34lat.jpg)
Stage 33-34, lateral view
1 day, 20 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 35 and 36; age 2 days, 2 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Stomodeal invagination roundish. Eye entirely black, choroid fissure nearly closed. Formation of two gill rudiments, anterior one nipple-shaped. Melanophores appearing on back. Posterior outline of proctodeum still curved. Length of tail bud about three times its breadth. Beginning of hatching. Length: 5.3 - 6.0 mm.](static/anatomy/NF/stage35-36lat.jpg)
Stage 35-36, lateral view
2 days, 2 hr pf @ 23°c
![Nieuwkoop and Faber stage 37 and 38; age 2 days, 5 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Stomodeal invagination much deeper, opening round. Both gill rudiments nipple-shaped, a branch of the anterior one indicated. Posterior outline of proctodeum straight, forming very obtuse angle with ventral border of tail myotomes. Melanophores spreading over tail. Length: 5.6 - 6.2 mm.](static/anatomy/NF/stage37-38lat.jpg)
Stage 37-38, lateral view
2 days, 5 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 39; age 2 days, 8 hr 30 min at 22-24 Celsius; corresponding to the following external morphological criteria: Melanophores appearing around nasal pits. Opening of stomodeal invagination transversely elongated. Melanophores on back arranged in a superficial and a deeper layer. Outlines of proctodeum and tail myotomes forming angle of about 135 degrees. Melanophores appearing along ventral edge of tail musculature. Length: 5.9 - 6.5 mm.](static/anatomy/NF/stage39latsmall.jpg)
Stage 39, lateral view
2 days, 8 hr 30 min pf @ 23°c
![Nieuwkoop and Faber stage 40; age 2 days, 18 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Mouth broken through. Length of gills about twice their breadth, posterior one sometimes also showing a branch. Outlines of proctodeum and tail myotomes forming angles of 90 degrees. Beginning of blood circulation in gills. Length: 6.3 - 6.8 mm.](static/anatomy/NF/stage40lat.jpg)
Stage 40, lateral view
2 days, 18 hr pf @ 23°c
![Nieuwkoop and Faber stage 41; age 3 days, 4 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Gills broader and flatter, more laterally directed. Formation of a left-rostral and a right-caudal furrow in yolk mass; torsion of interjacent part about 45 degrees; formation of conical proctodeum, forming angle of about 60 degrees with tail myotomes. Formation of fin rostral to proctodeum; ventral outline of yolk mass and proctodeum a smooth concave line. Length: 6.7 - 7.5 mm.](static/anatomy/NF/stage41lat.jpg)
Stage 41, lateral view
3 days, 4 hr pf @ 23°c
![Nieuwkoop and Faber stage 41; age 3 days, 4 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Gills broader and flatter, more laterally directed. Formation of a left-rostral and a right-caudal furrow in yolk mass; torsion of interjacent part about 45 degrees; formation of conical proctodeum, forming angle of about 60 degrees with tail myotomes. Formation of fin rostral to proctodeum; ventral outline of yolk mass and proctodeum a smooth concave line. Length: 6.7 - 7.5 mm.](static/anatomy/NF/stage41ventral.jpg)
Stage 41, ventral view
3 days, 4 hr pf @ 23°c
![Nieuwkoop and Faber stage 42; age 3 days, 8 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Beginning of formation of opercular folds. Torsion of intestine about 90 degrees; proctodeum connected with yolk mass by short horizontal intestinal tube. Length: 7.0 - 7.7 mm.](static/anatomy/NF/stage42lat.jpg)
Stage 42, lateral view
3 days, 8 hr pf @ 23°c
![Nieuwkoop and Faber stage 42; age 3 days, 8 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Beginning of formation of opercular folds. Torsion of intestine about 90 degrees; proctodeum connected with yolk mass by short horizontal intestinal tube. Length: 7.0 - 7.7 mm.](static/anatomy/NF/stage42ventral.jpg)
Stage 42, ventral view
3 days, 8 hr pf @ 23°c
![Nieuwkoop and Faber stage 43; age 3 days, 15 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Lateral line system becoming visible externally. Cement gland losing its pigment. Torsion of intestine about 180 degrees; proctodeum narrower, arched or S-shaped. Length: 7.5 - 8.3 mm.](static/anatomy/NF/stage43lat.jpg)
Stage 43, lateral view
3 days, 15 hr pf @ 23°c
![Nieuwkoop and Faber stage 43; age 3 days, 15 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Lateral line system becoming visible externally. Cement gland losing its pigment. Torsion of intestine about 180 degrees; proctodeum narrower, arched or S-shaped. Length: 7.5 - 8.3 mm.](static/anatomy/NF/stage43ventral.jpg)
Stage 43, ventral view
3 days, 15 hr pf @ 23°c
![Nieuwkoop and Faber stage 44; age 3 days, 20 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Appearance of tentacle rudiments. Opercular folds protruding further. Coiling part of intestine showing S-shaped loop; torsion about 360 degrees. Blood-circulation in gills usually ceased (gills smaller). Length: 7.8 - 8.5 mm.](static/anatomy/NF/stage44ventral.jpg)
Stage 44, ventral view
3 days, 20 hr pf @ 23°c
![Nieuwkoop and Faber stage 45; age 4 days, 2 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Operculum partly covering gills, edge still straight. Intestine spiralized in ventral aspects, showing 1.5 revolutions. Beginning of feeding. Length: 8 - 10 mm.](static/anatomy/NF/stage45lat.jpg)
Stage 45, lateral view
4 days, 2 hr pf @ 23°c
![Nieuwkoop and Faber stage 46; age 4 days, 10 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Edge of operculum becoming convex. Xantophores appearing on eye and abdomen. Intestine showing 2 to 2.5 revolutions. Hindlimb bud visible for the first time. Length: 9 - 12 mm.](static/anatomy/NF/stage46lat.jpg)
Stage 46, lateral view
4 days, 10 hr pf @ 23°c
![Nieuwkoop and Faber stage 46; age 4 days, 10 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Edge of operculum becoming convex. Xantophores appearing on eye and abdomen. Intestine showing 2 to 2.5 revolutions. Hindlimb bud visible for the first time. Length: 9 - 12 mm.](static/anatomy/NF/stage46ventral.jpg)
Stage 46, ventral view
4 days, 10 hr pf @ 23°c
![Nieuwkoop and Faber stage 47; age 5 days, 12 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Tentacles larger. Edge of operculum forming quarter of a circle. Xantophores forming opaque layer on abdomen. Intestine showing 2.5 to 3.5 revolutions. Hindlimb bud more distinct. Length: 12 - 15 mm.](static/anatomy/NF/stage47lat.jpg)
Stage 47, lateral view
5 days, 12 hr pf @ 23°c
![Nieuwkoop and Faber stage 47; age 5 days, 12 hr at 22-24 Celsius; corresponding to the following external morphological criteria: Tentacles larger. Edge of operculum forming quarter of a circle. Xantophores forming opaque layer on abdomen. Intestine showing 2.5 to 3.5 revolutions. Hindlimb bud more distinct. Length: 12 - 15 mm.](static/anatomy/NF/stage47ventral.jpg)
Stage 47, ventral view
5 days, 12 hr pf @ 23°c
![Nieuwkoop and Faber stage 48; age 7.5 days at 22-24 Celsius; corresponding to the following external morphological criteria: Beginning of pigmentation around n. acusticus. Forelimb bud visible for the first time. Shining gold-coloured abdomen. Hindlimb bud semicircular in lateral aspect. Length: 14 - 17 mm.](static/anatomy/NF/stage48lat.jpg)
Stage 48, lateral view
7 days, 12 hr pf @ 23°c
![Nieuwkoop and Faber stage 49; age about 12 days at 22-24 Celsius; corresponding to the following external morphological criteria: Melanophores usually appearing around thymus gland and nerves and blood vessels of head; xantophores appearing on pericard. Forelimb bud distinct. Hindlimb bud somewhat longer, distal outline still circular, no constrictions at base. Melanophores appearing on dorsal and ventral fin. Length: 17 - 23 mm.](static/anatomy/NF/stage49lat.jpg)
Stage 49, lateral view
12 days pf @ 23°c
![Nieuwkoop and Faber stage 49; age about 12 days at 22-24 Celsius; corresponding to the following external morphological criteria: Melanophores usually appearing around thymus gland and nerves and blood vessels of head; xantophores appearing on pericard. Forelimb bud distinct. Hindlimb bud somewhat longer, distal outline still circular, no constrictions at base. Melanophores appearing on dorsal and ventral fin. Length: 17 - 23 mm.](static/anatomy/NF/stage49ventral.jpg)
Stage 49, ventral view
12 days pf @ 23°c
![Nieuwkoop and Faber stage 50; age about 15 days at 22-24 Celsius; corresponding to the following external morphological criteria: Forelimb bud somewhat oval-shaped in dorsal aspect. Hindlimb bud longer than broad, constricted at base, distal outline somewhat conical. Length: 20 - 27 mm.](static/anatomy/NF/stage50lat.jpg)
Stage 50, lateral view
15 days pf @ 23°c
![Nieuwkoop and Faber stage 51; age about 17 days at 22-24 Celsius; corresponding to the following external morphological criteria: Tentacles much longer. Forelimb bud oval-shaped in lateral aspect. Hindlimb bud conical in shape, its length about 1.5 times its breadth; melanophores appearing on it. Length: 28 - 36 mm.](static/anatomy/NF/stage51lat.jpg)
Stage 51, lateral view
17 days pf @ 23°c
![Nieuwkoop and Faber stage 52; age about 21 days at 22-24 Celsius; corresponding to the following external morphological criteria: Forelimb bud irregularly conical. Hindlimb bud showing first indication of ankle constriction and first sign of flattening of foot. Length: 42 - 56 mm.](static/anatomy/NF/stage52lat.jpg)
Stage 52, lateral view
21 days pf @ 23°c
![Nieuwkoop and Faber stage 53; age about 24 days at 22-24 Celsius; corresponding to the following external morphological criteria: Fore- and hindlimbs in paddle stage. Hindlimb whithout foot somewhat longer than broad; 4th and 5th toe indicated. Length: 50 - 60 mm.](static/anatomy/NF/stage53lat.jpg)
Stage 53, lateral view
24 days pf @ 23°c
![Nieuwkoop and Faber stage 54; age about 26 days at 22-24 Celsius; corresponding to the following external morphological criteria: All four fingers indicated; edge of hand slightly scalloped between fingers; melanophores appearing on forelimb. Length of hindlimb without foot nearly twice its breadth; all five toes indicated, the second only very slightly. Length: 58 - 65 mm.](static/anatomy/NF/stage54lat.jpg)
Stage 54, lateral view
26 days pf @ 23°c
![](static/anatomy/NF/stage48-54limb.jpg)
Stage 48-54, limb buds
![Nieuwkoop and Faber stage 55; age about 32 days at 22-24 Celsius; corresponding to the following external morphological criteria: Hand pronated about 90 degrees; free parts of fingers about equally long as broad. Length of hindlimb without foot about 3 times its breadth; length of cartilages of 4th and 5th toe about 4 times their breadth. Length: 70 - 80 mm.](static/anatomy/NF/stage55lat.jpg)
Stage 55, lateral view
32 days pf @ 23°c
![Nieuwkoop and Faber stage 56; age about 38 days at 22-24 Celsius; corresponding to the following external morphological criteria: Elbow and wrist clearly indicated; length of free parts of fingers 3 to 4 times their breadth. Length of cartilages of 4th and 5th toe about 6 times their breadth. Length: 70 - 100 mm.](static/anatomy/NF/stage56lat.jpg)
Stage 56, lateral view
38 days pf @ 23°c
![Nieuwkoop and Faber stage 57; age about 41 days at 22-24 Celsius; corresponding to the following external morphological criteria: Pigment-free spot appearing above "Stirnorgan". Angle of elbow more than 90 degrees; fingers stretched out in forelimb atrium, their length about 7 times their breadth. Length: 75 - 105 mm.](static/anatomy/NF/stage57lat.jpg)
Stage 57, lateral view
41 days pf @ 23°c
![Nieuwkoop and Faber stage 58; age about 44 days at 22-24 Celsius; corresponding to the following external morphological criteria: Forelimbs broken through. Guanophores appearing on abdomen and thighs (adult skin areas). All three claws present on hindlimbs. Length: 80 - 110 mm.](static/anatomy/NF/stage58lat.jpg)
Stage 58, lateral view
44 days pf @ 23°c
![Nieuwkoop and Faber stage 59; age about 45 days at 22-24 Celsius; corresponding to the following external morphological criteria: Tentacles beginning to shrivel up. Stretched forelimb reaching down to base of hindlimb. Guanophores appearing near base of forelimb (adult skin area); anterior border of adult skin area on abdomen not yet sharp; appearance of irregular dark spots on back.](static/anatomy/NF/stage59lat.jpg)
Stage 59, lateral view
45 days pf @ 23°c
![Nieuwkoop and Faber stage 59; age about 45 days at 22-24 Celsius; corresponding to the following external morphological criteria: Tentacles beginning to shrivel up. Stretched forelimb reaching down to base of hindlimb. Guanophores appearing near base of forelimb (adult skin area); anterior border of adult skin area on abdomen not yet sharp; appearance of irregular dark spots on back.](static/anatomy/NF/stage59ventral.jpg)
Stage 59, ventral view
45 days pf @ 23°c
![Nieuwkoop and Faber stage 60; age about 46 days at 22-24 Celsius; corresponding to the following external morphological criteria: N. olfactorius still longer than bulbus olfactorius. Guanophores appearing on lower jaw (adult skin area). Openings of gill chambers still wide. Distal half of fingers of stretched forelimb extending beyond base of hindlimb; forelimb still situated behind level of heart. Adult skin area of base of forelimb covered with guanophores; anterior border of adult skin area on abdomen sharper, reaching up to heart.](static/anatomy/NF/stage60dorsal.jpg)
Stage 60, dorsal view
46 days pf @ 23°c
![Nieuwkoop and Faber stage 60; age about 46 days at 22-24 Celsius; corresponding to the following external morphological criteria: N. olfactorius still longer than bulbus olfactorius. Guanophores appearing on lower jaw (adult skin area). Openings of gill chambers still wide. Distal half of fingers of stretched forelimb extending beyond base of hindlimb; forelimb still situated behind level of heart. Adult skin area of base of forelimb covered with guanophores; anterior border of adult skin area on abdomen sharper, reaching up to heart.](static/anatomy/NF/stage60lat.jpg)
Stage 60, lateral view
46 days pf @ 23°c
![Nieuwkoop and Faber stage 60; age about 46 days at 22-24 Celsius; corresponding to the following external morphological criteria: N. olfactorius still longer than bulbus olfactorius. Guanophores appearing on lower jaw (adult skin area). Openings of gill chambers still wide. Distal half of fingers of stretched forelimb extending beyond base of hindlimb; forelimb still situated behind level of heart. Adult skin area of base of forelimb covered with guanophores; anterior border of adult skin area on abdomen sharper, reaching up to heart.](static/anatomy/NF/stage60ventral.jpg)
Stage 60, ventral view
46 days pf @ 23°c
![Nieuwkoop and Faber stage 61; age about 48 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head narrower. Tentacles considerably shortened, mostly curved backwards. Length of n. olfactorius equal to diameter of bulbus olfactorius. 4th arterial arch seen just in front of adult skin area of forelimb. Openings of gill chambers considerably narrowed. Forelimb at level of posterior half of heart. Adult skin area on abdomen covering posterior half of heart. Fins considerably reduced.](static/anatomy/NF/stage61dorsal.jpg)
Stage 61, dorsal view
48 days pf @ 23°c
![Nieuwkoop and Faber stage 61; age about 48 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head narrower. Tentacles considerably shortened, mostly curved backwards. Length of n. olfactorius equal to diameter of bulbus olfactorius. 4th arterial arch seen just in front of adult skin area of forelimb. Openings of gill chambers considerably narrowed. Forelimb at level of posterior half of heart. Adult skin area on abdomen covering posterior half of heart. Fins considerably reduced.](static/anatomy/NF/stage61lat.jpg)
Stage 61, lateral view
48 days pf @ 23°c
![Nieuwkoop and Faber stage 61; age about 48 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head narrower. Tentacles considerably shortened, mostly curved backwards. Length of n. olfactorius equal to diameter of bulbus olfactorius. 4th arterial arch seen just in front of adult skin area of forelimb. Openings of gill chambers considerably narrowed. Forelimb at level of posterior half of heart. Adult skin area on abdomen covering posterior half of heart. Fins considerably reduced.](static/anatomy/NF/stage61ventral.jpg)
Stage 61, ventral view
48 days pf @ 23°c
![Nieuwkoop and Faber stage 62; age about 49 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head still somewhat broader than cranial part of trunk. Tentacles short, straight. N. olfactorius shorter than diameter of bulbus olfactorius. Corner of mouth still in front of eye. Thymus gland somewhat protruding. 3rd arterial arch (\"larval aorta\Select") seen at distance of its own diameter in front of adult skin area of forelimb. Opening of operculum reduced to curved slit. Forelimb at level of middle of heart. Anterior border of adult skin area on abdomen entirely sharp, mostly nicked medially. Ventral fin disappeared from abdomen.](static/anatomy/NF/stage62dorsal.jpg)
Stage 62, dorsal view
49 days pf @ 23°c
![Nieuwkoop and Faber stage 62; age about 49 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head still somewhat broader than cranial part of trunk. Tentacles short, straight. N. olfactorius shorter than diameter of bulbus olfactorius. Corner of mouth still in front of eye. Thymus gland somewhat protruding. 3rd arterial arch (\"larval aorta\Select") seen at distance of its own diameter in front of adult skin area of forelimb. Opening of operculum reduced to curved slit. Forelimb at level of middle of heart. Anterior border of adult skin area on abdomen entirely sharp, mostly nicked medially. Ventral fin disappeared from abdomen.](static/anatomy/NF/stage62lat.jpg)
Stage 62, lateral view
49 days pf @ 23°c
![Nieuwkoop and Faber stage 62; age about 49 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head still somewhat broader than cranial part of trunk. Tentacles short, straight. N. olfactorius shorter than diameter of bulbus olfactorius. Corner of mouth still in front of eye. Thymus gland somewhat protruding. 3rd arterial arch (\"larval aorta\Select") seen at distance of its own diameter in front of adult skin area of forelimb. Opening of operculum reduced to curved slit. Forelimb at level of middle of heart. Anterior border of adult skin area on abdomen entirely sharp, mostly nicked medially. Ventral fin disappeared from abdomen.](static/anatomy/NF/stage62ventral.jpg)
Stage 62, ventral view
49 days pf @ 23°c
![Nieuwkoop and Faber stage 63; age about 51 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head narrower than trunk. Tentacles mostly disappeared. Corner of mouth at level of caudal border of eye. \"Larval aorta\" and thymus gland no longer externally visible. Operculum closed. Adult skin areas on abdomen and lower jaw separated by narrow band of larval skin. Forelimb at level of anterior half of heart. Fin mostly perforated near anus. Tail still slightly longer than body.](static/anatomy/NF/stage63dorsal.jpg)
Stage 63, dorsal view
51 days pf @ 23°c
![Nieuwkoop and Faber stage 63; age about 51 days at 22-24 Celsius; corresponding to the following external morphological criteria: Head narrower than trunk. Tentacles mostly disappeared. Corner of mouth at level of caudal border of eye. \"Larval aorta\" and thymus gland no longer externally visible. Operculum closed. Adult skin areas on abdomen and lower jaw separated by narrow band of larval skin. Forelimb at level of anterior half of heart. Fin mostly perforated near anus. Tail still slightly longer than body.](static/anatomy/NF/stage63ventral.jpg)
Stage 63, ventral view
51 days pf @ 23°c
![Nieuwkoop and Faber stage 64; age about 53 days at 22-24 Celsius; corresponding to the following external morphological criteria: Corner of mouth well behind eye. Various adult skin areas joined almost everywhere, borderlines still clearly visible. Length of tail (from anus) is a third of body length.](static/anatomy/NF/stage64dorsal.jpg)
Stage 64, dorsal view
53 days pf @ 23°c
![Nieuwkoop and Faber stage 64; age about 53 days at 22-24 Celsius; corresponding to the following external morphological criteria: Corner of mouth well behind eye. Various adult skin areas joined almost everywhere, borderlines still clearly visible. Length of tail (from anus) is a third of body length.](static/anatomy/NF/stage64ventral.jpg)
Stage 64, ventral view
53 days pf @ 23°c
![Nieuwkoop and Faber stage 65; age about 54 days at 22-24 Celsius; corresponding to the following external morphological criteria: Borderlines between adult skin areas partly disappeared. Tail oblong triangular in dorsal aspect, length abouth one tenth of body length.](static/anatomy/NF/stage65dorsal.jpg)
Stage 65, dorsal view
54 days pf @ 23°c
![Nieuwkoop and Faber stage 66; age about 58 days at 22-24 Celsius; corresponding to the following external morphological criteria: Border lines between adult skin areas disappeared. Tail only a very small triangle, no longer visible from ventral side.](static/anatomy/NF/stage66dorsal.jpg)
Stage 66, dorsal view
58 days pf @ 23°c