Normentafeln zur Entwicklungsgeschichte der Wirbelthiere. 
Brain and Cephalic Nerves 
Spinal Cord. Spinal Nerves. Sympathetic 
| Cephalic end of medullary plate raised up, broad. Here medullary groove 
wide open but somewhat deeper than in No. 650: it does not extend entirely 
to anterior end of medullary plate. 
| Essentially like No. 621, Table 4. 
Medullary tube extends to anterior border of head, where tube is open. In 
| region of optic diverticula, a narrow dorsal opening of medullary tube; in 
| tube. 
of future hind-brain. 
Medullary tube open at anterior end of head, and ventrally under region of 
| optic diverticula: closed dorsally and separated from dorsal ectoderm in regions 
of fore-, mid- and hind-brains; the latter show beginning differentiation and 
| expansion. Fore-brain, excepting optic diverticula, shows little expansion. An- 
lagen of trigeminal and acoustico-facial ganglia ? 
tube distinct ventrally under region of optic diverticula. Fore-, mid- and hind- 
roughly triangular in cross section, base dorsal. 
2 Anlagen of trigeminal and 
acoustıco-facial ganglia quite clear. 
Essentially like No. 619, Table 6. 
siderably expanded. Anlagen of trigeminal and acoustico-facial ganglia. Anlage 
of glossopharyngeal ganglion ? 
Fore-brain considerably expanded, extends anterior to optic vesicles. Narrow 
its thin ependymal roof developed somewhat. Trigeminal and acoustico-facial 
ganglia distinct, the former a little larger than the latter. Probable glosso- 
pharyngeal ganglionic anlage just posterior to otocyst, much smaller and less 
distinct than the two anterior. Possible indistinct anlage of vagus ganglion? 
F4 
Fore-brain and mid-brain a littie more expanded than at 9'/, days. Narrow 
|region between mid-brain and hind-brain, or isthmus, somewhat differentiated. 
Hind-brain most expanded in region of 5th ganglion,; here thin ependymal 
roof widest; quite clear division of wall of hind-brain into dorsal and ventral 
zones of Hıs. Trigeminal ganglion large and prominent. Acoustico-facial 
ganglion distinct but not so large as trigeminal. Small anlage of glosso- 
pharyngeal ganglion. Small indistinet anlage of vagus ganglion? 
| Fore-brain extends some distance anterior to optic vesicles.. Narrow region 
| between fore-brain and mid-brain. Mid-brain circular in cross section. Isthmus 
| quite distinct, oval in cross section. 5th ganglion large and prominent. A division 
|of 5th ganglion extending cephalad, ophthalmic? 7th and 8th ganglion large. 
Glossopharyngeal ganglion distinct but smaller than the two cephalad of otocyst. 
Vagus ganglion less distinct than gth. In region of ıoth ganglion hind-brain 
| much less expanded than in region of sth ganglion. Slight Varolian bend. 
| Early hemisphere anlagen as small lateral projections from wall of fore-brain. 
| Mid-brain nearly circular in cross section. Isthmus distinct, oval in cross section, 
\elongated dorso-ventrally. 5th ganglion large and prominent. Ophthalmic 
ı division of 5th ganglion, extending cephalad. 7th and 8th ganglion large and 
| prominent but smaller than sth. gth ganglion distinct but slender, much smaller 
than 7th and $th. ıoth ganglion distinct. In region of 7th and 8th ganglion, 
| wide thin ependymal roof of hind-brain: a trace of division of walls of latter 
|into dorsal and ventral zones; furrow between ventral zones. Small Rand- 
schleier ventrally. 
Small hemisphere anlagen only slightly more distinct than at ıı days. Fore- 
| brain extends well anterior to optic stalks. Anlage of motor oculi nerve, as a few 
\fibers from ventral region of mid-brain. In region of 5th ganglion, ventral 
|zones :of hind-brain nearly level with each other; beginning mantle layer; 
small Randschleier. Motor root of 5th nerve evident. Ophthalmic division 
\of 5th ganglion extends dorsal to eye. Beginning mandibular division of 
|5th ganglion? gth ganglion distinct. Beginning differentiation of ganglion jugulare 
and nodosum of Ioth nerve, the latter more distinct than the former. Distinct 
fibers of Ioth nerve. Spinal accessory anlage. Distinct fibers of hypoglossal 
nerve. Varolian bend a gradual curve. 
Anlagen of hemispheres distinct. Beginning differentiation of EHRENRITTER’S 
ganglion and ganglion petrosum of gth nerve. In general esentially like ıı!/, day 
embryos. 
|region probably of future mid-brain, dorsal ectoderm closed over medullary 
Medullary tube has a narrow dorsal opening in region of posterior part 
| 
Fore-brain, excepting optic diverticula, not much expanded. Hind-brain con- 
Medullary groove wide open throughout. In region of segments, medullary 
groove deeper than more cephalad. Medullary plate thicker than adjoining 
ectoderm, rather abrupt demarcation between the two. No medullary 
groove over anterior end of primitive streak, but small medullary plate. 
Medullary groove wide open throughout. In future cardiac region and region 
of segments, a sharp demarcation between medullary plate and adjoining 
ectoderm. Caudad of segments, no such sharp demarcation. No medullary 
groove but small medullary plate over anterior end of primitive streak. 
Essentially like No. 621, Table 4. 
In region of first segment, medullary tube open dorsally: through 2 and 3 
segments tube closed dorsally but not separated from dorsal ectoderm; 
through 4 segment tube open dorsally by a narrow fissure; through 
5 segment dorsal ectoderm closed over tube; tube open between 5 and 6 
segments and from that point caudad. 
Dorsal ectoderm closed over medullary tube in region of anterior segments. 
Medullary tube open dorsally in region of posterior segments and thence 
caudad. Abrupt demarcation between dorsal ectoderm and that of 
medullary tube in region of posterior segments. Shallow medullary 
groove over primitive streak. No medullary groove over posterior end 
| of medullary plate, under caudal amnion. 
Medullary tube not open at anterior end of head. Seam of closure of medullary | 
Dorsal ectoderm closed over medullary tube caudad of segments and 
h | under caudal amnion, but only in anterior part of this region; in posterior 
brains more clearly differentiated and expanded than in No. 620. Hind-brain | 
part, medullary tube open dorsally by a narrow fissure: here abrupt 
demarcation between medullary and dorsal ectoderm. Medullary groove 
deep and narrow over primitive streak; narrow dorsal opening. Shallow 
| medullary groove appears to reach posterior end of medullary plate. 
Medullary tube closed dorsally but not separated from dorsal ectoderm 
near anterior end of primitive streak. 
Small medullary tube, open dorsally, over posterior end of remnant of ' 
primitive streak. Probable anlagen of spinal ganglia in trunk, but not „ 
distinet, merely small clusters of cells. 
{ , 1 L t > | In heart region, medullary tube elongated dorso-ventrally; cavity narrow. 
region between fore-brain and mid-brain. Hind-brain considerably expanded; | 
Dorsal and ventral walls thinner than lateral. Medullary tube completely 
formed to tip of tail. Probable spinal ganglionic anlagen, but not distinct 
structures. 
In region just posterior to heart, medullary tube elongated dorso-ventrally, 
oval in cross section, cavity narrow. Medullary tube, completely formed, 
extends to tip of tail, ending blindly; here tube is small, circular in cross 
section. Rather indistinct anlagen of spinal ganglia; these are more 
distincet in posterior part of trunk than in region just caudad of brain. 
In region posterior to heart, spinal ganglia quite distinct. Here medullary . 
tube elongated dorso-ventrally, narrow from side to side, with narrow 
cavity. A trace of Randschleier. Caudad medullary tube gradually 
becomes less differentiated. 
In heart region, distinct spinal ganglia. Spinal nerve formed by junction 
of dorsal and ventral roots, which now appear. Distinct fibers in spinal 
nerve, which extends a short distance only. In region of anterior limb 
buds, ventral roots traceable but less distinct than more cephalad. In 
region of posterior limb buds, no distinct dorsal ganglia. 
In cervical region, ventral roots and spinal nerves very small; dorsal 
ganglia distinct. In region of anterior limb buds, spinal cord elongated 
dorso-ventrally; roughly quadrilateral with rounded edges in cross section; 
cavity narrow especially between ventral zones; distinct roof and floor 
plates; larger ventral, smaller dorsal zones: small Randschleier; distinct 
mantle layer in ventral zones. Spinal nerve fibers extend to root of 
anterior limb bud. In region of posterior limb buds, spinal nerves not 
formed; dorsal ganglia visible, though not large; no distinct mantle layer. 
In caudal region, no distinct dorsal ganglia. 
Essentially like ı1ı!/, day embryos. 
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