No. 2.] SPINNING ACTIVITIES OF PROTOPLASM. 369 
In many of these dishes it was difficult later to find any eggs 
which had not reached a normal, free-swimming, larval state 
due at about that given time. The test specimens were kept 
isolated of course, but compared with results given by random 
specimens from the larger number. 
In the eggs of Arbacia, I had seen the characteristic, striated 
membrane produced, immediately after entrance of the sperm, 
by formation of innumerable, delicate, thread-like processes 
from a clear pellicular layer of the egg. Although the 
resemblance between these threads and those formed in the 
tuft of protoplasm which receives the sperm was very great, 
I could not convince myself that they were not perhaps 
of non-living matter and caused by mere exudation of a.glairy 
substance, which, if issuing from small, pore-like openings, 
could assume a thread-like shape. An appearance of partial 
return in single instances of the substance towards the egg, did 
not seem proof to the contrary, since it was thought that this 
would be quite possible were the substance of the nature 
suggested. 
In the Echinus eggs, the question seemed to be solved by 
several cases of polyspermy, in which the egg, seen to be 
immature from the nuclear conditions, never formed a perfect 
membrane, but merely made abortive attempts to do so, the 
various portions of its surface having more or less success, 
or making, perhaps, more or less exertion, in spznning. Of 
the most typical instance of this sort, a camera lucida memo- 
randum was made, showing the various protoplastic activities 
of the pellicular substance, and also the several tufts which 
mark the entrance, complete or partial, of several sperm. 
The whole surface of this egg, soon after entrance of the 
first sperm, was covered with a rather thick and albuminous- 
looking material, like ectosarcal protoplasm, in which no vesic- 
ular structure of Biitschli was visible, although there was a 
deceptive appearance of such, caused, as it seemed, by optical 
sections of papillose, or short, thread-like, processes. 
This clear layer seemed at first to be only partially effective 
in preventing the entrance of more sperm, and it responded to 
the attempts of these with more or less pronounced tufts, and 
