Normentafeln zur Entwicklungsgeschichte der Wirbelthiere. 
Age 
— 
Spinal Cord. Spinal Nerves. Sympathetic 
Eye 
121, 
‚In region of heart, mantle layer of ventral zones of spinal cord quite pro- 
days | minent: spinal nerve extends to level of dorsal border of dorsal aorta. Anlage 
| of sympathetic chain? a little cluster of darkly stained cells dorsad of dorsal 
|aorta, on each side of embryo. Spinal nerve extends to root of anterior limb 
|bud. Spinal nerve, rather indistinct, extends to root of posterior limb bud. 
In this region mantle layer of ventral zones is very small; dorsal ganglia are 
small. Spinal nerves not formed caudad of posterior limb buds. Dorsal 
|ganglia rather indistinct in caudal region. 
ventrally, distinct roof and floor plates; spinal nerve has small dorsal ramus. 
| Sympathetic chain anlage in cervical region. Spinal nerve extends into anterior 
limb bud, where it branches. Spinal nerve extends into posterior limb bud. 
|In cervical region, mantle layer of spinal cord large, mostly in ventral zone; 
| narrow cavity; small oval bundle; Randschleier thicker ventrally; small dorsal 
ramus of spinal nerve; distinct anlage of sympathetic chain. In region of 
posterior part of heart, ramus communicans from spinal nerve to sympathetic 
chain; spinal cord in essentially the same condition as in cervical region. 
Spinal ganglia are level with ventral region of spinal cord. A trace of sym- 
| pathetic.chain anlage in region of posterior limbs. Small dorsal ganglia 
|and small spinal nerves in caudal region. 
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In cervical region, spinal cord has distinct roof and floor plates; narrow 
|cavity, elongated dorso-ventrally; large mantle layer extending dorsally. 
| Ventral zones slightly protuberant. Randschleier thicker ventrally. Sym- 
pathetic chain with fibers. In heart region, spinal cord in essentially same 
| condition as in cervical region. Ramus communicans from spinal nerve to 
|sympathetic chain. Distinet anlage of pia mater. In tip of tail, spinal cord 
merely an epithelial tube oval in cross section. 
Spinal cord in a condition very similar to that of I5-day embryos. Ramus 
| communicans from spinal nerve to sympathetic chain in region of posterior 
| limbs. 
| In cervical region, dorsal zones have begun to grow together dorsally; central 
canal shorter than at 16 days. Ventral horns quite prominent; also dorsal 
|horns, but less so than ventral; small ventral fissure. In region of anterior 
limbs and of stomach, also of posterior limbs, spinal cord in essentially the 
same condition as in cervical region. 
In cervical region, central canal of spinal cord still quite long; ventral horns 
more prominent than at 16'/, days; ventral fissure deeper. Toward tip of 
tail, spinal cord merely an epithelial tube oval in cross section. 
In cervical region, central canal of spinal cord smaller than at 17 days, dorsal 
zones have grown together more; dorsal and ventral horns quite prominent; 
ventral fissure quite deep. In region of heart, spinal cord a little more 
slender than in cervical region. In region of lower border of stomach, spinal 
cord broader than in heart region. 
In cervical region, central canal of spinal cord small, oval in cross section; 
dorsal zones have grown together greatly; ventral horns broad, prominent; 
also dorsal horns; ventral fissure small. In region of heart, spinal cord more 
slender, narrower laterally than in cervical region. In abdominal region, 
caudad of stomach, spinal cord more square in cross section; hence adult 
characteristics of cervical, thoracic and lumbar cord. In tail, spinal cord 
merely an epithelial tube. 
In cervical region, spinal cord has long central cavity, quite large mantle layer | 
Lentic vesicle completely closed; its inner wall distinctly thicker than outer, 
which is closely applied to external ectoderm. Secondary optic cup clearly 
formed. Retinal anlage distinctly thicker than anlage of pigment layer. 
Cavity of primary optic vesicle very small. Distinct retinal pigment, though 
small in amount. Choroid fissure distinct in optic stalk, near optic cup. 
No fissure in optic stalk near brain. Optic stalk hollow. 
Cavity of lentic vesicle small; its inner wall much thickened; cells of this 
wall elongated. Small amount of mesenchyma between lentic vesicle and 
external ectoderm. Walls of secondary optic cup closed ventrally. Distinct 
choroid fissure in optic stalk near optic cup. Cavity of optic stalk much 
smaller than at ı2!/, days. Prolongation of optic stalk, with blood vessel, 
arteria centralis retinae, included, through cavity of primary optic vesicle, 
now very small. Distinct retinal pigment. A little vascular tissue between 
lens and retinal anlage. 
Cavity of lentic vesicle nearly obliterated by thickening of its inner wall. 
In this embryo, no retinal pigment. 
Cavity of lentic vesicle nearly obliterated by thickening of its inner wall, 
whose cells are elongated. A little mesenchyma between lentic vesicle and 
external ectoderm. Secondary optic cup completely closed ventrally. Distinct 
retinal pigment. Retinal anlage close to pigment layer. Optic stalk quite 
long but small in cross section, with small cavity. A little vascular tissue 
between lens and retina. 
Lens, large, fills mouth of optic cup. Fibers of lens distinct. Retinal anlage 
quite thick. Dark retinal pigment. Optic stalk quite long, of small cross 
section; cavity of stalk partly obliterated. A trace of fibers in stalk. Space 
| between lens and retina, the future chamber of vitreous humor, small; contains 
vascular tissue. Anlagen of some ocular muscles. Anlagen of lids. 
A layer of mesoderm between lens and external ectoderm. Lens for the 
most part inside optic cup. Lens fibers conspicuous. Retinal anlage at margin 
of optic cup thin. Optic stalk solid; contains numerous fibers. Beginning 
|of optic commissure. Anlagen of ocular muscles. Anlagen of eyelids. Lach- 
ırymal duct anlage? solid. 
| Quite thick mesoderm between lens and external epithelium. Lens fills mouth 
of optic cup. External wall of lens a thin epithelium. Retinal anlage thin at 
| margin of optic cup. Distinct retinal pigment. Optic stalk (nerve) quite 
|large, mostly fibers. Numerous fine fibers in anlage of vitreous humor. 
| Distinct hyaloid artery running to inner surface of lens. Optic commissure 
| more distinct. Lachrymal duct anlage? solid. Eyelids small. Distinct ocular 
muscle anlagen. 
Anlage of vitreous humor quite vascular. Distinct non-nucleated zone in 
retina next to anlage of vitreous. Optic nerve quite large, mostly fibers. 
| At point of entrance of optic nerve into eye, hyaloid artery is enclosed in 
|nerve. Optic commissure more distinct than at 16'/, days. Lachrymal duct 
anlage solid. 
Large lens fills mouth of optic cup. Distinct lens epithelium. Lens fibers 
| more, nuclei less conspicuous than in younger embryos. Anlage of vitreous 
mostly fine fibers with a few blood vessels. Optic commissure well marked. 
Hyaloid artery enclosed in optic nerve at point of entrance of latter into 
eye; the artery leaves the nerve just beyond the eye. Lachrymal duct anlage 
mostly solid. Lids larger than at 17 days. 
Anterior chamber formed, hence anlage of cornea differentiated. Very thin 
pupillary membrane. Quite abrupt thinning of retina at margin of optic cup 
indicating ora serrata. Anlage of vitreous humor mostly fine fibers with a 
few small blood vessels. Distinct fibers running between retina and optic 
|nerve. Hyaloid artery runs to inner surface of lens. Optic commissure and 
tracts distincet. Dense retinal pigment. Lachrymal duct has in part a cavity. 
Lids joined together. 
