GJIOWTII OF EGGS AND EGG-STRINGS IN NEPUELIS. 189 



On the Origin and Growth of the Eggs a?id Egg-strings 

 in Nephelis, with some Observations on the " Spiral 

 Asters/' By Isao Iijima, of the University of Tokio. 

 With Plates XV[, XVII, XVIII, and XIX. 



The following investigation was begun in the spring of 

 1880, and continued through the summer of the following 

 year. Its entire course was completed in the Zoological 

 Laboratory of the University of Tokio, under the instruction 

 of Professor Whitman. To his advice, never-failing en- 

 couragement, and unremitting efforts to render this work as 

 complete as time and circumstances would permit, I must 

 ascribe much of whatever success I may have achieved. 



My thanks are also due to the authorities of the Univer- 

 sity for the use of instruments and other means of carrying 

 on my investigation, and especially to the President of the 

 University, Mr. Kato, for permission to continue my work 

 during the summer vacation. 



For books of reference I have consulted the University 

 Library and also that of Professor Whitman, to whom I am 

 again deeply indebted for having put all his books at my 

 disposal. But I wish to make it here known that I could 

 not get access to some few works more or less connected 

 with my subject. In the absence of such works, I hope the 

 reader will find a sufficient excuse for any omission of due 

 references which may have crept in. However, I have tried 

 to make these references as complete as circumstances seem 

 to require by the aid of citations found in those books at 

 my command. Such references will be noted by an asterisk 

 in the list given at the end of this paper. 



My investigation has been confined to a species of 

 Nephelis, probably a variety of N. vulgaris, Moq.-Tand. It 

 is the only Nephelis found in this city, and is the most 

 abundant representative of the Hirudinea found in Japan. 



Methods of Investigatmi. 



1. For examination of the genital organs in a fresh con- 

 dition, specimens were killed either by chloroforming or by 

 plunging into chromic acid (| per cent.). They were pinned 

 in a black wax trough containing water, or a salt solution 

 (I per cent.) when swelling was to be avoided, and opened 

 by a lateral incision, so that the dorsal body-wall could be 

 removed. For certain purposes, it is advantageous to allow 



