Normal Plates of the Development of Lepidosiren paradoxa arid Protopterus annectens. 



15 



Hypophysis 



Enteron 



NotochorJ 



Visceral clefts 



Splanchno- 

 coele 



Urogenital System 



Heart and Vessels 



Stage 



Foregut becoming 

 folded off from rast 

 of endoderm by j 

 small Space devel 

 oping beneath its 

 anterior end. 



(Separated from 

 endoderm, circular 



in transverse 

 section , cells flat 



and plate-like. 



Primary sheath lias 



appeared.) 



(Ingrowth 

 just cora- 

 mencing.) 



Foregut well folded 



off from rest of 



endoderm. 



(Six solid cleft ru 

 diments. Last two 

 not yet completely 

 fused with ecto 

 derm.) 



Anus closed. 



Anus closed. 



Six solid cleft rudi 

 ments. 



21 



(Pronephric tubules 



developing; pro- 

 nephric Chambers not 

 continuous; duct 

 does not reach 

 cloaca.) 



23 



Spacious 



pericardiac 



cavity, two 



halves fused 



except be 



hind. 



Pronephros with two 

 funnels. Pronephric 

 Chambers continuous. 

 (Glomerulus still in 



two segmental 



pieces ) Archinephric 



ducts are open into 



cloaca. 



Heart rudiment 

 with a few cor- 

 puscles free in 

 lumen. Vessels of 

 external gills also 

 apparent and with 

 a few corpuscles. 



25 



Cleft rudiments 

 solid. 



(Glomus no longer 

 segmented.) Archi- 

 nephric duct tortuous 

 towards its front 

 end. 



(Dorsal aorta, as 



solid heavily 

 3'olked rudiment.) 



Archinephric duct 



coiled in region of 



pronephros. 



Dorsal aorta with 



lumen and scat- 



tered corpuscles 



27 



28 



