No. 2.] THE DEVELOPMENT OF THE NEWT. 317 



Polyspermy has been described also by Oppel ('92) in the rep- 

 tilian Qgg {Angids, Tropidoiiotus). His results agree strik- 

 ingly with those of Riickert, although presenting many inter- 

 esting points of difference. Here, as in the Selachians, a 

 number of spermatozoa normally penetrate the tgg. They 

 develop into full-fledged sperm nuclei which divide caryo- 

 kinetically, though very sluggishly and irregularly, and soon 

 abort. 



There is, hence, wide variation in the phenomena of fertil- 

 ization among vertebrates, (i) Only a single spermatozoon 

 normally enters the ^gg [Teleost (Trout), Bohm ; Amphibia 

 (Rana), Born, Roux]. (2) Many spermatozoa normally enter 

 the Qgg, in which case they may {a) develop into nuclei which 

 divide caryokinetically and regularly (^Selachians, Ruckert); 

 or ip) they develop into nuclei which divide slowly and with 

 many abnormalities, and soon degenerate {Rcptilia, Oppel) ; 

 or (c) they develop into nuclei which speedily degenerate with- 

 out undergoing division {Dieniyctylus). 



One thing is certain : such physiological polyspermy as 

 has been described here is a usual occurrence in the eggs of 

 many vertebrates. This establishes the important fact that 

 the mere entrance of several spermatozoa into an ovum exerts 

 no injurious influence upon development. This being true, 

 it follows that the more frequent case of the admission of 

 only a single sperm is probably to be regarded as due to the 

 conditions of nuclear attraction rather than to any necessity 

 for barring the way against superfluous spermatozoa. It is 

 not that an excess of spermatozoa is harmful, but that the 

 female nucleus is satisfied, as it were, with the entrance of 

 one, and no longer acts so attractively upon those outside. 

 The fact that several spermatozoa enter an ^gg which has 

 been weakened by rough treatment or overripeness shows 

 that the internal conditions of the Qgg cell have been altered, 

 but shows nothing more. The abnormal development that 

 follows cannot be regarded as purely the result of the super- 

 fertilization, but both events, the abnormal development as 

 well as the entrance of several spermatozoa, are direct con- 

 sequences of the internal disturbances in the ^gg. The normal 



