No. 2.] THE EGG OF BUFO LENTIGINOSUS. 335 



does not have, in all cases, the morphological value that has 

 been ascribed to it. 



VI. Polyspermy. 



It cannot be doubted that polyspermy occurs in many eggs 

 which subsequently undergo a perfectly normal development. 

 Foot ('94) has found it in the &g2, of Allolobophora, Oppel ('92) 

 in the reptilian q.%%, Ruckert in the selachian Qg^, and van der 

 Strict ('95) in the Qgg of Amphioxus. According to Jordan, Fick, 

 Kupffer, Braus, and Michaelis, polyspermy is also normal in 

 the amphibian ^gg. Born, differing from the last two observ- 

 ers, has maintained that but one spermatozoon normally enters 

 the Qg% of Triton, and Roux has made the same statement 

 regarding the frog's Q.gg. Although Kupffer observed several 

 spermatozoa entering the living Q.gg of Bufo variabilis, my own 

 results are not in accord with these. In the examination of a 

 large number of both normally and artificially fertilized eggs, I 

 have never found a single o.'gg containing more than one sper- 

 matozoon. I am inclined to believe, therefore, that the eggs 

 observed by Kupffer were undergoing pathological changes 

 permitting the entrance of several spermatozoa, and that poly- 

 spermy is not a normal occurrence in the q.%^ of Bufo. 



Summary. 



1. The unripe ovarian egg of Bufo lentiginosus is surrounded by four 



membranes. The first and second are a part of the epithelium of 

 the ovary; the other two, the chorion and the inner yolk-membrane, 

 belong to the &gg ; beneath them perivitellin is found. 



2. The three kinds of nucleoli in the ovarian egg disappear at the end of 



maturation. 



3. The ovarian egg contains twenty- four separate chromosomes. These 



are at first composed of rod-shaped microsomes, later they have a 

 filamentous structure, and at the end of hibernation each appears to 

 be composed of a single series of rounded microsomes. 



4. Before the disintegration of the germinal vesicle begins, a portion of 



the egg cytoplasm near the lower pole of the nucleus forms a 

 fibrous band — the beginning of the line of radiation. 



5. The nucleoplasm apparently forms the rays that run into the line of 



radiation after the breakina: down of the nuclear membrane. 



