Self -Fertilization Induced by Artificial Means. 153 



dividual — is double, the halves being united at the distal end. 

 Owing to the close proximity of the ovary to the surrounding 

 tubes of the testis, it is possible only by very careful manipulation 

 to get the eggs out of the cavity of the ovary without cutting into 

 the testicular tubes. When it was necessary to separate the eggs 

 from the sperm of the same individual, I have carried out this 

 operation, but in general the ovaries and the testes were cut up 

 together. 



For the purpose of studying the effects of self-fertilization 

 Cynthia is in many respects inferior to Ciona because self-fer- 

 tilization takes place to a very large extent. On the other hand, 

 if check experiments are use'd for each individual, this factor can 

 be estimated, and the very fact that Cynthia does self-fertilize 

 its own eggs to such an extent gives an opportunity to examine 

 other aspects of the problem. A much more serious difficulty 

 is met with in that artificial cross-fertilization is often unsuccessful 

 in this species. Even when the eggs and sperm from a large 

 number of individuals are mixed together, fertilization may not 

 take place; but in curious contrast to this result are the following 

 observations on the egg-laying processes of this animal kept in 

 aquaria. On several occasions a number of individuals were put 

 together in the same dish. About 5 o'clock in the afternoon one 

 after another began to send out jets of eggs and of sperm pro- 

 ducing the effect of a lively cannonading. Under these circum- 

 stances it was found that every single egg was fertilized. Perhaps 

 only ripe individuals sent out their eggs and sperm, or perhaps the 

 eggs were mature in all individuals, and the sperm from one or 

 two individuals may have sufficed to fertilize all of the eggs. In 

 general it is, I think, the sperm of Cynthia that is not good. 

 Certainly the spermatozoa are often very sluggish when taken 

 from the testis and put into water. May it not be possible that 

 when the eggs are laid, Cynthia secretes some other fluid that 

 makes the sperm active? This point needs further investigation. 



The best means that I found to determine the extent to which 

 self-fertilization of the eggs of Cynthia may take place was to 

 isolate some of the individuals early in the day, and observe in 

 those that emitted eggs and sperm in the late afternoon the per- 



