120 



A. OKA. 



polyzoöid. This mode, however, heems t(j take place Nerv rare]y, if 

 ever, in the present species. 



By the second mode, germs enchjsed in hard chilinous cases 

 (statoblasts) are produced in the funicuhir cavity of polyzoöids. 

 They are set fi-ee by the decay of the parent cohjny, and float on the 

 surface of water during" winter, sometimes packed in ice. Next sum- 

 mer a primary polyzoöid is developed in each, serving as a foundation 

 for a new colony. Thus, this and tlie first mode perform tlie same pur- 

 pose, in so far as both serve to establish new colonies, and the with- 

 drawal of the latter is supplanted l)y the great activity of the foriner. 



By the third mode, a certain part of the endocyst adds, by 

 growth in a certain definite manner, new polyzcjüids to the primary 

 polyzoöid. This mode of reproduction increases the size and de- 

 termines the form of the colony. 



In certain cases the colony may propagate itself by simple divi- 

 sion. For instance, Allman and Hyatt observed that in old colonies 

 of such genera as CV/6'f((f6'//(/, Lophopus iiuû FectiiiatcU't, all of which 

 have gelatinous ectocyst, the branches separate themselves from the 

 cœnœcial trunk by constriction. In Feet, (lelafinosa, however, I 

 have never met with the same phenomena. On the contrary, all the 

 ("olunies collected by me shc^wed no sign of such fissiparity, all of 

 them being entire and of the form characteristic to this species. In 

 most of them, the shell-halves of the statoblast in which the primary 

 polyzoöid has developed were seen sticking to the underside some- 

 where about the centre. 



With regard to the first mode of reproduction, I had no chance 

 of making observations any further than determining the j)resence of 

 ovaries in certain polyzoöids. The phenomena of reproduction by 

 the remaining two modes shall be treated, for sake of convenience, 

 under the followini»' four heads: 



