JOURNAL OF THE COLLEGE OP SCIENCE, IMPERIAL UNIVERSITï, 

 ^ TOKYO, JAPAN. 



VOL. XX., ARTICLE 1. 



On the Formation of the Germinal Layers 

 in Gastropoda. 



Bv 



T. Fujita, R{^nhushi. NogaJuishi. 



With 3 plates. 



In spite of tlie foct that within recent years the morphogenesis 

 of the Mollusca has received a. great deal of attention from 

 embryologists, there is still much disagreement among authors 

 with regard even to some of the fundamental points in the early 

 phases of development. This is no doubt due to actual differences 

 in developmental processes found in the various animals employed 

 for investigation, and this makes it highly desirable to extend 

 our researches to as many different forms as possible, if we are 

 to arrive at any comprehensive results in these vexed problems. 

 With this aim in view I first paid a great deal of attention to 

 the early development of the Gastoropoda, Siphonaria lepida 

 Gould. A preliminary note on that subject was published in the 

 Tokyo Zoological Magazine, Vol. VIL, No. 79, 1895. A few 

 years later I undertook a similar investigation on another form, 

 Ajjlysia sp. The conclusions reached in the latter study were 



