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 by way of suggestion and kindly criticism. 
MATERIAL AND METHODS. 
For the material upon which this study has been made, | 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. They 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 purely 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 hematoxylin 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 Conklin. 
