y8 T. H. MORGAN, F. PAYNE, ETHEL N, BROWNE. 



the outermost layer of the egg. As a rule a pause follows, and 

 it may take the spermatozoon from five to twenty minutes to 

 disappear within the egg. The penetration is, as a rule, at first 

 slow but later the spermatozoon may enter quite suddenly. 

 Whether the sperm bores its way into the egg, or whether there 

 is first a reaction between the surface of the egg and the sperma- 

 tozoon so that the egg also takes a part in the process need not 

 be discussed here, but it is important to note that no spermato- 

 zoa enter except those that stand with their long axis vertical 

 to the surface and pierce the surface with the tip of the sperm 

 head. 



Our observations show that the first sperm that fulfills these 

 conditions is received. In some of these cases a second sperm 

 came in contact with the egg after the first had come in contact 

 with it. In all such cases the first sperm only penetrated. 

 There was no evidence in favor of selective fertilization, since in 

 all forty cases the first sperm that approached in the normal posi- 

 tion was the first to enter. It is highly improbable that forty times, 

 this first sperm was the one suited to enter (assuming that two 

 kinds exist) when there is no evidence that the eggs attract the 

 sperm. Our general conclusion from the data here presented is 

 that in this case selective fertilization does not occur, and since 

 Cumingia is unisexual the temptation is to generalize this state- 

 ment to include all such forms. Whether this extension is war- 

 rantable or not the fact remains that in this, the only case so far 

 tested, the evidence is opposed to the hypothesis of selective 

 fertiHzation. 



Columbia Univer.mty, 

 November 20, 1909. 



