Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. 



Stage 



Series 



Length 



Age 



34 



175 Trans. 



180 Sag. 



181 Front. 



35 



182 Trans. 



183 Sag. 



184 Front. 



36 



21 mm 



22 mm 



49 days 



Axis of head, trunk 

 and tail coincide with 

 line slightly arched up- 

 ward overyolk. Yolk 

 elongated, narrowed 

 dorso-ventrally; narro- 

 west portion anterior; 

 viewed from above 

 pear-shaped, narrow 

 end anterior. Tailvery 

 wide dorso-ventrally. 

 Irregulär band of pig- 

 ment along side of 

 body. Anterior limbs 

 project postero-ven- 

 trally three digits for- 

 med. Posterior limbs 

 ]iroject caudad. 



52 days 



Body Form 



Somites 



Notochord 



186 Trans. 

 188 Sag. 

 191 Front. 



23 mm 



55 days 



Caudal portion filamentous 

 with slight knob at extreme 

 end ; still rests against neural 

 tube. Mesenchymal thicken- 

 ings in sheath present in 

 caudal portion. 



Nervous System 



Eye 



Ear 



Flexures less marked. 

 Hemispheres extendi 

 far in front of dien- 

 cephalon. Epiphysis 

 and paraplu'sis large. 

 Plica rhombomesen-' 

 cephalica well defined. 



Lamina cerebellaris 



Short; commissura 

 superior and posterior 



and habenularis all 

 well developed. Spinal 



ganglia very large. 



Nerves well devel- 

 oped. 



Anterior end of notochord 

 separated from hypophysis 

 by thinlayerof mesenchyma. 

 Surrounded by very dense 

 membrane. Slightlj' con- 

 stricted at level of mesen- 

 chymal condensations indi- 

 cating boundaries of verte- 

 brae. Indications of ossi- 

 fication in sheath. Anlage 

 of haemal arches in anterior 

 portion of tail. 



Ganglionic layers 

 of retina marked 

 off from inner layer; 

 layer of rods and 

 cones indicated by 

 layer of elongated 

 celis. Pigment pro 

 miiient in iris. Epi- 

 thelium of lens flat 

 on outer surface, 

 cuboidal on inner, 



Paraphysis shows few 



lateral diverticula. 

 Ganglion habenulare 

 and tuberculum pos- 

 terius well defined. 

 Commissura cerebel- 

 laris formed, also 

 commissura anterior 

 and commissura pallii 

 anterior. Layer of 

 fibrous matter around 

 cord thicker. Band of 

 cells on dorsal border 

 of cord larger, dorsal 

 half of central canal 

 nearly closed. Pia 

 mater better defined. 



Does not quite reach poste- 

 rior end of neural tube. Yolk 

 absorbed except at extreme 

 anterior end. Sheath strongly 

 developed. Constrictions 

 better marked. Neural 

 arches developed throughout 

 body; meet dorsally in trunk 

 region but not in tail. Ossi- 

 fication beginning in ante- 

 rior neural arches. Haemal 

 arches better defined in tail. 

 Where neural processes are 

 given off notochord is com- 

 pressed laterally giving it 

 a triangulär outline in cross 

 section. 



Rods and cones 

 recognizable. Iris 

 more deeply pig 

 mented; lies close 

 against epithelium 

 oflens. Optic nerve 

 well differentiated ; 



still contains 

 minute lumen near 

 eye. Anlage of 

 Cornea as single 

 layer of mesen- 

 chymal cells. 



Utriculo-saccu- 



lar partition 

 extends about 

 half way across 

 vesicle. Semi- 

 circular canals 



partially en- 

 closed in carti- 

 lage. Periotic 

 capsule entirely 

 surrounds ear. 



Rods and cones 

 better defined; 

 outer and inner 

 nuclear layers in 

 dicated ; ganglionic 

 layer well defined. 

 Pigment dense in 



retina and iris; 

 some pigment in 

 choroid. Lens epi 



thelium flatter. 

 Sclerotic indicated 

 band of dense 

 mesenchyma. 



