No. 420.] HISTORY OF STICHOSTEMMA. 997 
in their history. Moreover, eggs and spermatozoa leave the 
gonads together when the eggs are laid. By subjecting the 
animal to pressure the spermatozoa may often be seen in 
the same gonads with fully grown oócytes, and when the egg 
leaves the body there are nearly always a considerable number 
of spermatozoa sticking to its membrane. The contact with 
the water apparently serves as a stimulus, and fertilization as 
well as maturation occurs very soon after the egg leaves the 
body. : 
From these relations it is evident that self-fertilization is 
possible. As a matter of fact it is undoubtedly the rule. In 
a large number of cases specimens which had been isolated for 
a week or two laid eggs, and these were always fertilized and 
developed. I have often removed the eggs artificially by cut- 
ting the animal into pieces, and in every case where fully 
grown eggs were present, fertilization occurred. The fully 
grown eggs can be distinguished by the fact that no peduncle 
of attachment is present. In younger eggs the membrane is 
incomplete, and the egg is in continuity with the protoplasm of 
the gonad through a small stalk or peduncle. I have never 
been able to obtain unfertilized eggs. Finally, sections of the 
animal with full-grown egg cells always show the spermatozoa 
clustered over the surface of the egg or massed in some part of 
the gonad, while specimens with younger egg cells show stages 
of spermatogenesis, and still younger stages show merely the 
young oócytes and the sperm mother-nuclei. The spermatozoa, 
or some of them, always pass out with the egg, and I believe 
that each egg is fertilized by the spermatozoa of the same 
bsolutely no evidence that spermatozoa 
gonad. There is a 
None have ever been 
reach the oócytes in any other manner. | 
found in the slime which encloses the egg after it is laid in 
None have been found in the water in 
which many specimens had been kept. But I think the strong- 
est evidence in favor of self-fertilization lies in the fact noted 
above, that spermatozoa can be seen upon the membrane of 
each egg cell and that the penetration of these spermatozoa 
can be observed immediately after the egg cell reaches the 
water. Asin S. eilhardi, the genital pores are not preformed, 
the normal manner. 
