On the Breeding Habit and Development of 



Nereis japonica n. sp. 



BY 



Akira Izuka. 



Assistant Professor of Zoology, Imperial University, Tokyo. 



The Lycorid Annelid dealt with in this paper comes very close to 

 Nereis diversicolor O. F. Müll., as compared with the descriptions and 

 drawings of the latter given by several authors (Malmgren, Ehlers and 

 Schröder, &c.) and also with the alcoholic specimens* from St. Andrews 

 (Scotland) and from Foxfield in the Dudden estuary (England). However 

 there exist some differences between the two forms, mainly in the arrange- 

 ment of paragnathi. Thus in the Japanese specimens the paragnathi in 

 the VII. and VIII. divibion of the proboscis are arranged in one continuous 

 row, while in N. diversicolor they are arranged in three or four irregular 

 rows (text-figure i, A and B.) ; and moreover the falcate bristles of the 

 former are of a greater magnitude than those of the latter (text-figure i, C 

 and D.) 



The eyes of the former are provided with a distinct lens in each, 

 while there is no lens to be found in those of the latter. The breeding 

 habit of the Japanese worm also differs from that of N diversicolor. I am 

 thus led to consider the former to represent a new species, which shall be 

 named 



Nereis japonica n. sp. 



* I beg here to express my thanks to both Px'ofessor M'Intosh and Mr. C. Crossland 

 (or their kindness in sending me the specimens referred to Nereis diversicolor Mull. 



