IÓ2 



DR. IWAJ] IKEDA. 



ordinary category of Hydrozoan asexual reproduction. 



Judging from the stages I lia ve collected, the buds of the present 

 species may be said to be practically of the same structural plan as 

 Corymorpha palma described by Torrey. It is very much to be regreted 

 that the present investigation could not be extended to the early stages 

 of the bud development. 



The earliest stage (fig. 5) that came under my observation is 

 about 1.3 mm. long. It already shows the; definitive shape of a hyd- 

 rosome ; both the hydrocaulus and hydranth are well diffenentiated. 

 The former is, as already remarked, provided with four distal 

 and seven proximal tentacles, but is as yet without any gonosomal 

 rudiment ; the latter shows four longitudinal canals each ending 

 proximally with a rudimentary papilla. Sections of the stage 

 show conditions sumilar to what Torrey has described of the 

 corresponding stage of young C. palma. The hydranth-cavity is alrcdy 

 divided into the upper (hypostomal) and the lower cavity by the 

 characteristic endodermal septum ; also a second septum, the fenestrated 

 membrane of the adult, is already present but is not yet perforated. 

 A point worth mentioning is that even in such an early stage there 

 is the rudiment of the free-cell forming structure located just above 

 the insertion of the septum. There one notices a narrow zone (about 

 20 fi in width) of the hypostomal endoderm, which is represented by 

 a remarkably thin epithelium (about 6/t thick) consisting of a row of 

 cubical and deeply staining cells (5-7 in a longitudinal section). As 

 the buds grow larger, both sorts of tentacles gradually increase in 

 number ; so also the longitudinal canals and the papillae on hydro- 

 caulus. In an intermediate stage bearing seven distal and fourteen 

 proximal tentacles, a single gonosome was found in the incipient 

 condition, there being present the definitive mouth and the perforated 

 membrane while the longitudinal canals numbered as yet only four. 

 The rudiment of the lymphoid <. stucture remians in this stage , in 

 nearly the same state as in the youngest stage -observed; by me, 



