No. 3.] SFERMATOPHORES. 369 



"These facts raise a suspicion that Clepsine is capable of self- fecun- 

 dation. The question as to whether copulation occurs will be most 

 satisfactorily settled by isolating young individuals and keeping them 

 until they produce eggs. 



May 2, 1878. — " Five individuals were isolated in the summer of 

 1877, at the time of hatching. Each has been kept in a separate vessel 

 from that time to the present, f^ggs were laid by one April 24th (this 

 year), and hatched May ist ; by two others, April 29th. The latter are 

 now in the germ-band stage. The eggs had in each case passed the 

 pronuclear stage, at the time they were first noticed, so that I was unable 

 to demonstrate by section the existence of a male pronucleus. As the 

 eggs developed in the normal manner, it is very probable that they were 

 fecundated. Here is an unquestionable case of self-fructification, or of 

 parthenogenesis — more probably the former." 



The above statements not only confirm the observation of 

 Filippi and Grube, as to isolated individuals producing fertile 

 eggs, but they also make it probable that fertilization is inter- 

 nal. To the evidence given by eggs taken artificially from 

 the ovaries, I can nov/ add another which seems to be perfectly 

 conclusive. I have succeeded in finding a perfectly distinct 

 and indubitable male pronucleus in the ripe ovarian &%g of C. 



marginata. 



What I formerly regarded as positive proof, either of self- 

 fructification or of parthenogenesis, in the light of what I now 

 know about the use of spermatophores, is open to some doubt. 

 At the time of my experiment of rearing individuals from the 

 &g^ in isolation, the possibility of hypodermic impregnation 

 never crossed my mind, and I can now see where my observa- 

 tion was not sufficiently guarded to remove all doubt. In order 

 to bring the five individuals to maturity, I had to feed them 

 some ten or twelve times. I allowed them to take their meals 

 from the same fish, only thinking it necessary to watch them 

 from beginning to end, in order to see that no copulation took 

 place. Whether I ever allowed them to come in contact long 

 enough to deposit spermatophores, my notes do not show, and 

 here is where the doubt comes in. The experiment ought to be 

 repeated under conditions that would exclude every possibility 

 of contact, and C. vmrgijiata would be one of the best species 

 for such a purpose, as it is so easily reared. It would be well 

 to isolate a large number of individuals, so as to have material 



