1904.] NATURAL SCIENCES OF PHILADELPHIA. 327 



University, as well as throughout the two intervening summers at the 

 Woods Hole Marine Biological Laboratory. 



I am glad to acknowledge the many courtesies extended to me at 

 both institutions. I am particularly indebted to Prof. Conklin, at 

 whose suggestion the work was undertaken, and it is a pleasure to ex- 

 press here my sincere appreciation of the valuable assistance which 

 he has given me bj^ way of suggestion and kindly criticism. 



Material and Methods. 



For the material upon which this study has been made, I am 

 indebted to Drs. E. G. Conklin and M. A. Bigelow, by whom it was 

 collected at Woods Hole, Massachusetts, during the summers of 1897 

 and 1898. The Nudibranchs were found spawning upon floating 

 gulf-weed in Vineyard Sound, taken to the Laboratory and kept in 

 aquaria for some weeks, where they spawned prolifically and where, 

 from day to day, the eggs were collected and preserved. Tliey were 

 fixed in Kleinenberg's stronger picro-sulphuric solution and Boveri's 

 picro-acetic for one-half to three-quarters of an hour and washed in 

 50 and 70 per cent, alcohol, as is the usual custom. Living material 

 upon which to study the breeding habits of the animals has not been 

 accessible to me, though search has been made in the same locality 

 during the last two summers. This lack of the living adult animals 

 and embryonic stages has been a considerable drawback, as it is par- 

 ticularly desirable that one investigating the developmental history of 

 an organism should be able to observe its physiological activities and 

 thereby verify conclusions gained through pureh' morphological work. 

 The material at hand has been amply sufficient for carrying the work 

 up to the stage of the free-swimming veliger, but not to the metamor- 

 phosis. It is my hope that in the near future material for the study 

 of later stages and of the metamorphosis into the adult may be 

 obtained, as many questions relative to the fate of larval organs must 

 remain unanswered until this be accomplished. 



Contrary to the conditions found among some other Nudibranchs, 

 the gelatinous mass surrounding the egg-capsules does not become 

 greatly hardened upon fixing, for upon being brought into water the 

 jelly usually dissolves, leaving the eggs free in their individual capsules. 

 The eggs may be sectioned without removing the jelly, as it cuts 

 without difficulty. Both whole mounts and sections were stained in 

 Delafield's hsematoxylin diluted with six to ten times its volume of 

 distilled water and slightly acidulated by the addition of a trace of 

 HCl, or Kleinenberg's stronger solution after the method of ConkHn. 



