Z K. MITSTTKUHr. 



tio-ate the whole history of these nicmbraiu's in thi« oroup. The 

 following embodies the resiihs of my sf udy km\ tliis subject. 



The species which I have iiivestigatxMl are C le mm y s (or 

 Emys) Japonica, Gray, and Tri onyx Ja))onicus , Schlegel. 

 In earlier stages, the fetal meml)ranes of these two species are very 

 much alike ]3ut in later stages they present differences which, in my 

 oj)inion, are highly significant. F«H' convenience of trentment. I shnll 

 divide the present article into three parts, ns follows : — 

 I. Earlier Stages of the Amnitin, 

 11. Origin of ihe Allantois. 

 ni. Later Stages of the Fœtal Membranes. 



And in (»ach part, 1 shall tivat the two spe(äes sej)aratel y, generally 

 giving th<' description of CI em my s first, as that species seems to 

 have more primitive relations in its fœtal membranes. At the conclu- 

 sion, 1 have put together some suggestions on the theoretical bearings 

 (»(' the Cacf^ l)foii<jli( fordi inidef tlie liead of (General Considerations. 



I. Earlier Stages of the Amnion. 



a. Clciiwni^ Japonica. 



The first stage of which 1 shall give a description is re))resented 

 in siirfi<e view in Figs. ]. and 1 a. Fl. I. There is at tins period a 

 deep horse-shoe shaped groove bounding the anterior end of the em- 

 bryonic region — the "Vordere (Jrenzfurche " of Cerman authors* 

 The posterior wall of this groove is the head of the eml)ryo, while its 

 anterior wall is the first rudiment of the anterior fold of the 

 amnion. T'he structure and relations of these parts will become 

 clear from the sections to be described directly. The medullary 

 groove is still open thoughout its length, its posterior pai't being 

 wi<ler apart than its anterior poi'tion. The dorsal opening of the 



