252 whitman: . [Vol. I. 



productions, and hence the argument from analogy falls to the 

 ground. When Kupffer or any other investigator succeeds in 

 showing, under perfectly normal conditions, that more than one 

 spermatozoon is concerned in the formation of the male pronu- 

 cleus, we shall be ready to concede that a case of polyspermatic 

 fecundation has been established. Decisive evidence can be 

 obtained in no other way than by tracing the history of the 

 male pronucleus, and it is precisely in this direction that 

 Kupffer's observations are most incomplete. 



Kupffer claims also " Copulationshiigel " and polyspermatic 

 fecundation for the amphibian egg and the lamprey Q:^<g. He 

 has seen the hiigel penetrated by spermatozoa, but has failed to 

 determine their fate, and thus left it entirely uncertain whether 

 more than one of them is concerned in the act of fecundation. 

 Through the investigations of Bambeke, O. Hertwig, Roux, and 

 Born, the history of the male pronucleus in the amphibian &^^ 

 has been very completely ascertained. Thus far no positive 

 evidence has been produced to show that the male pronucleus 

 is the product of several spermatozoa. The indications are 

 plainly in favor of monospermatic fecundation. If several sper- 

 matozoa took part in fecundation we should expect to find a 

 corresponding number of pigment paths. Referring to this 

 point, Roux (4, p. 173) remarks : " Van Bembeke fand wieder- 

 holt mehrere solchcr Pigmentstrassen im Ei, wahrcnd ich in 

 etwa 100 geschnitteiien Eicrn dies bios cinmal beobacJitct tind 

 dies Ei stammte voin Elide der LaicJiperiodc, wo Abnormit'dten 

 scJir li'diifig sind. Mcine U)itcrsiicJmngcn bcst'dtigcn also die 

 Angaben von O. Hertwig iind Boi'n, dass normaler Weise bios 

 ein Samcnkorper in das Ei eindringt." 



With reference to the place of penetration, O. Hertwig (i, p. 

 82) makes the following statement: " Bei Rana temporaria 

 erfolgt der Eintritt des befruchtenden Spermatozoon in den 

 Dotter stets a7?t scJiwarzen Pol ziir Scite des scJileierformig aiis- 

 gebreitetcn Excretkorpcrs auf der vom Eikern abgewandten 

 Eihalfte." Roux admits that the spermatozoon generally enters 

 the egg near the upper pole, but denies that this is invariably 

 the case (4, p. 174). 



