The Early Development of the Pigeon's Egg. 25 



vicinity is fertilized, but we may suppose that the cytoplasm in the 

 peripheral and deeper parts of the germinal area retains its in- 

 fluence and attracts the supernumerary sperm nuclei into itself 

 just as the cytoplasm of the unfertilized egg attracted the spermatozoa 

 at the time of fertilization. 



All of the reported cases of polyspermy in animals are for eggs 

 containing a large amount of yolk, or else those whose peculiar form 

 places much of their cytoplasm at some distance from the egg nucleus. 

 ''The union of the germ-cells calls forth profound changes in both" 

 (Wilson, '00, p. 200). Many monospennic eggs are so small that 

 the profound physiological change caused by the entrance of a 

 spermatozoon is almost immediately effective in every part of the 

 egg. Or, indeed, the immediateness of the effect of fertilization may 

 be due in some cases to the character of the protoplasm rather than 

 to the small size of the egg. The germinal area of the pigeon's egg 

 in a state of maturation presents a diameter of about 3 mm. on the 

 surface, and is 0.25 mm. deep in the central part. (These measure- 

 ments are from sections of the egg shown in Chart I and Figs. 2 and 

 3). Considering the size, and expanded form of the germinal area, 

 and possibly also some peculiarity inherent in the protoplasm of the 

 pigeon's egg, one may suppose that the peripheral and deeper parts 

 of the cytoplasm retain their attractive power for an appreciable time 

 after the entrance of the spermatozoa into the central superficial 

 region of the germinal area. 



If we may then accept these two hypotheses: (1) of the attractive 

 influence of unfertilized cytoplasm upon spermatozoa, and (2) the 

 temporary retention of that influence in parts of the pigeon egg 

 distant from the egg nucleus after the entrance of the spermatozoa ; 

 then we may conclude: (1) that the supernumerary sperm nuclei 

 migrate because of the attraction of the cytoplasm on them, and 

 (2) the path of migration of each nucleus is the resultant of the 

 attractive forces acting upon it. These two conclusions will, I think, 

 explain the position of the supernumerary sperm nuclei in the pigeon 

 and selachian. 



The spermatozoa enter the egg in the vicinity of the egg nucleus. 

 Since their number varies, their distribution also varies in different 



