The Early Development of the Pigeon's Egg. 23 



Polyspei-my in the Neiut. — In the egg of the newt, supernumerary 

 sperms degenerate early. Jordan ('93) found them in the four- 

 celled stage, but not later. 



Polyspermy in Reptiles. — Oppel ('92) found the reptile agreeing 

 with the Selachian in respect to the sperm origin of the super- 

 numerary nuclei, but in the Selachian they lead to the merocytes, 

 and in the reptile after a few divisions they remain rudimentary 

 (Oppel, '92, p. 282). Oppel agrees with Eiickert that on general 

 principles he cannot believe that the "ISTebenspermakerne" enter into 

 the structure of the future embryo (Oppel, '92, p. 283). 



In the Kreuzotter (Pelias berus Merr) Ballowitz ('03) found 

 "Nebenspermiumkenie" in the maturation stages. He believes that 

 they give rise to the "Paraspermiumkerne" of later cleavage, and 

 these correspond to Eiickort's merocyte nuclei. But Ballowitz says 

 that Eiickert's merocytes are derived from sperm nuclei, and that 

 he regards as periblast nuclei only those in the marginal cells remain- 

 ing in contact with the yolk. Ballowitz, on the other hand, derives 

 the periblast nuclei from daughter nuclei remaining in the yolk 

 and derived from blastomeres. He designates them as "oogenetisch." 

 But he thinks it possible that one of the deep parasperm nuclei may 

 turn back to the floor of the cleavage cavity and remain there as a 

 "spermogenetischen Periblastkern" (Ballowitz, '03, p. 84). The 

 usual origin of the periblast nuclei is the cleavage nuclei. He thinks 

 the parasperm nuclei play no considerable role in the development 

 of the germ. But if they come into the coarse yolk under better 

 conditions of nourishment, they may divide and in certain circum- 

 stances be added to the germ layers. 



Polsypermy in Birds. — Harper ('04) established the fact of poly- 

 spermy in the pigeon, but did not determine the fate of the super- 

 numerary sperm nuclei. It has been shown in an earlier part of 

 this paper (p. 13) that in the pigeon's egg, the supernumerary sperm 

 nuclei disappear about ten or twelve hours after fertilization, before 

 or soon after the 32-celled stage. In maturation stages they migrate 

 out of the blastodisc into the periblast, and the longer they remain 

 there, the more definitely they become separated from the blastodisc 

 by planes of cleavage. This fact suggests that they do not enter 



