Further Studies on the Formation of the 

 Germinal Layers in Chelonia. 



(Contributions to the Embryology of Reptilia III). 



By 



K. Wlilsukuri, Ph. D., Riéakuhakushi. 

 Professor of Zoology, Science College, Imperial University, Tokyo, Japan. 



With Plates II.— IV. 



Some yenrs ago conjointly with Mr. Ishikawa, I published a paper 

 on the Formation of the Germinal Layers in Chelonia (No. 1). Our 

 observations were then made solely on Trionyx japonicus, 

 Schlegel. Recently I have had an opportunity of studying the earlier 

 stao-es in the development of CI em my s jnponicn. Grnij. The 

 results of my observations in tlie latter species confirm onr vicavs on 

 all essential points. Jn addition. I have been nble to elucidnte more 

 fully the earlier phases in the formation of the mesobJast not only in 

 Clemmvs l^ut also in Trionyx. These, in my opinion, lead to 

 conclusions of considerable importance and deserve the attention of 

 those who are engaged in the study of the vertebrate development. 



The materials for the investigation were as before obtained from 

 tortoises which breed freely in captivity. As each deposit of e^^r^ 

 was marked as it was' laid, I had an unusual opportunity of obtaining 

 a complete series of embryos. In some cases, T took egg^ out of one 

 deposit at several different times, in order to determine more ac- 



