158 T.H.Morgan. 



A few preliminary experiments showed that the sperm of Mol- 

 gula fertilizes the eggs of the same individual. The -following 

 illustrations will show the great powers of self-fertilization of 

 this species: 



These cases make it clear that the sperm is capable of fer- 

 tilizing the eggs of the same individual. Whether the sperm 

 of another individual is prepotent I did not attempt to determine. 

 There were only a few cases in which neither self- nor cross- 

 fertilization was effective, and whenever good crossing was accom- 

 plished self-fertilization was also realized, showing that when the 

 sperm is good, it will readily fertilize the eggs of the same 

 individual. Since similar results were obtained when three in- 

 dividuals were used it will not be necessary to give the latter 

 cases. The experiments were not extensive enough to show whether 

 good sperm affects the eggs of certain individuals better than it 

 does others, but Molgula is not well suited to test this point. 



It occurred to me as possible that in Cynthia and in Molgula 

 the power to self-fertilize the eggs might be due to the eggs 

 coming from the ovary on one side of the body, and the sperm 

 from the other side. Conversely, if this were true, the lack of 

 self-fertilization in Ciona might be connected with the presence 

 of only one ovo-testis. I examined this possibility for Molgula. 

 The eggs from the small ovo-testis were fertilized with sperm 

 from the same side, and other eggs with the sperm from the other 

 side. In both cases all the eggs were fertilized. Conversely, the 

 eggs from the large ovary were fertilized with sperm from the 



1 In B the sperm was probably bad. The Ab must therefore have been self- 

 fertilized. The same conditions hold also for the second couple. 



