2 AKT. 3. S. IKEDA I CONTRIBUTIONS 



(1). The blastopore is closed by the coalescence of the 

 lateral lips (Concrescence theory), and the fundamental parts 

 of the embryonic body are formed upon the lower hemisphere 

 of the egg. (Pflüger, Koux, Hertwig, Morgan, et al.). 



(2). The blastopore is closed, mostly by the overgrowth 

 of the ventral lip, and the fundamental parts of the embryonic 

 body are formed upon the upper hemisphere of the egg. 

 (O. Schulze, and others who accept the old views). 



(3). The blastopore is closed by the overgrowth of the 

 dorsal, ventral, and lateral lips, and the fundamental parts 

 of the embryonic body are formed, partly upon the upper, 

 and partly upon the lower hemisphere of the egg. (Asshe- 

 ton, Kopsch, Eycleshymer, et al.). 



As is well known, the facts on which the views of many 

 of these writers are based, were obtained either from experi- 

 mental study or from abnormally developing eggs (spina bifida, 

 etc.). It has always seemed to me that one ought to exercise 

 extreme caution in making use of this class of facts and that 

 after all, the best way of studying normal processes of develop- 

 ment would be to study normal eggs by some method which 

 would not interfere with the normal course of events. For some 

 years past I had thought that the eggs of our Rhacophorus 

 schlegcUi would furnish peculiarly favourable material for the 

 investigation of the questions under discussion. As I have 

 already stated in my former paper, 1 ' the eggs of this animal are 

 absolutely without pigment, and among other favorable peculiari- 

 ties, allow the invagination cavity L to be seen through faintly. 

 The " Wachsthumsrand " or the "Equatorial Zone" comparable 

 to the " Germinal Ring " of the fish-egg, may be recognized 



1) Annotationes Zoological Japonenses, Vol. I. Part 1II.,^(1897). 



