250 



T. IKE DA : 



ment. I think it highly probable that the relative extent of rhynchocoel 

 in the four specie; also varies inversely with the s'ze of each; that 

 is, it should be of the largest extent in the smallest form, and 

 vice versa. But this can not certainly be insisted upon without exact 

 measurements of the organ in all the known species. 



The Life -habits. 



As to the original habitat of the plant, Lysichiton kamtschatense, 

 I have made some inquiries, in view of the possibility that the 

 animals were transported together with the plant from somewhere to 

 the garden. But I could receive no satisfactory information, except 

 that the plant is a form indigenous in Hokkaido as well as in some 

 parts in the north of the Main Island or Honshu. Anyway, it seems 

 certain that this Japanese species of Stichostcmma belongs to the 

 temperate-subarctic fauna as do also all the known species (St. eil~ 

 hardi from Berlin, St. asensoriatuin from Pennsylvania, and St. 

 g race use from Gratz). 



As to the life-habit of the species in the plant-vessel, they were 

 always found buried 1-2 cm. deep in the very soft mud and almost 

 always in a contracted state within the mucous secreta, — never found 

 creeping on the bottom, nor swimming in the water. The worms 

 showed a fairly strong tendency to negative heliotropism, so that, 

 when kept in a small vessel, they crept about on the surface of mud 

 during night or early in the morning, but went underneath the mud 

 when bright sun-shine pervaded the room. They are more or 

 less gregarious, as often observed by me in the culture-vessels and in 

 the plant- vessel. Most of the specimens in hand were dug out from 

 among the plant-roots, where they were found crowded together. 



The negative heliotropic habit of the worms seems to be directly 

 related with the nocturnal spawning. During nearly 70 days, from 

 the 19th of April to the end of June, I have observed twenty or more 

 cases of spawning but never in the day-time. Judging from the fact 



