22 



Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. 



Stage 



Series 



Length 



Age 



Body Form 



Somites 



Notochord 



Nervous System 



Eye 



Ear 



40 



206 Trans. 



207 Sag. 

 209 Front. 



27 mm 



67 days 



41 



210 Trans. 



211 Sag. 



212 Front. 



28 mm 



70 days 

 4 hrs. 



General coutour of 

 body much chan- 

 ged, owing to rapid 

 absorption of yolk. 

 Tail broader dorso- 



ventrally. Con- 

 stricted at level of 



posterior limbs. 



Yolk very long 

 oval, flatter on ven- 

 tral surface. Pig- 

 mentation extend- 



ing down over 

 one half of lateral 



surface of yolk. 



42 



213 Trans. 



214 Sag. 

 216 Front. 



2g mm 



74 days 

 12 hrs. 



4.3 



217 Trans. 



218 Sag. 



219 Front. 



30 mm 



78 days 



In anterior 

 trunk region 



myotomes 

 wider occupy- 

 ing nine tenths 

 of Space be- 

 tween noto- 

 chord and skin; 



extend ven- 

 trally to median 

 line where they 

 coalesce. 



Chorda more com- 

 pressed laterally at 

 points where neural 

 arches come in con 

 tact. In trunk region 

 and in region of pos- 

 terior limbs transverse 

 diameter equals that 

 of spinal cord; in tail 

 region diameter twice 

 as great as that of 

 cord. Beginning ossi 

 fication in haemal 

 arches. 



Much constricted in 

 region where carti- 

 lages are in contact 

 with body of verte-; 

 brae. Thickenings of 

 sheath to form inter-, 

 vertebral disks betterj 

 marked. Cartilagesj 

 lie between layer of 



bona and sheath. 

 Ossification beginning 

 in lateral basal pro- 

 cesses. Cartilaginous 

 ribs present. 



Brain and cord nearly in 

 straight line. Groove pre- 

 sent between diencephalon 

 and mesencephalon. Deep 

 groove in front of cerebelluni 

 Plexuses large filling greater 



portion 01 3'''^ ventricle 

 extending into lateral ven- 

 tricles and into 4'!' ventricle. 

 Distal end of paraphj'sis lies 

 on level with epiphj'sis. All 

 commissures better defined. 

 Brain fills brain case at an- 

 terior end, not posteriorly. 

 Spinal cord does not nearly 

 fill canal. Dorsal columns 

 of cord well defined; gray 

 commissure present between 

 them and gray matter of 

 cord. Central canal very 

 small, circular in section 



Ear much extended 

 antero-posteriorly 

 compressed dorso- 

 ventrally. Ossification 

 beginning in external 

 portion ofotic capsule. 



Endolvmphatic sac 

 wider; duct narrower. 

 Cristae acusticae of 

 canals formed. Macula 



acustica sacculi a 

 thickened area of epi- 

 thelium three rows 



deep. Semicircular 



canals enclosed in 

 cartilage. Ossification 



more extended on 



lateral surface of peri- 



otic capsule. 



