66 TT''. B. K'h'khani — Maturation of the Egg of the While Mouse. 



cal inHuence of the spermatozoon upon the egg, such influence being at 

 first limited to tlie germinal vesicle. In the rabbit he distinguished 

 a large number of cleavage stages, while in the dog he made the 

 fundamental observation that the Qo^'g at the time of heat lies in the 

 Fallopian tube, ovulation being here independent of copulation. 

 His studies on the ^gg of the guinea-pig established the fact that in 

 this animal the eggs mature just after parturition. Only a few 

 stages of the deer's ^gg were seen by Bischoff, but he found that 

 the eggs in the Fallopian tube have their development arrested dur- 

 ing the winter. 



Reichert ('6l) also studied the ii<^g of the guinea-pig, and found, 

 as Bischoff ('52) had observed, that while these animals are in heat 

 immediately after parturition, ovulation takes place only after coitus, 



Weil ('73) worked with rabbit's eggs, and found that these 

 animals, like guine9.-pigs, are in heat immediately after parturition. 

 This observer was probably the first to perceive both the male and 

 female pronucleus in a mammalian o.^^. 



Van Beneden ('75) was the first investigator to undertake histo- 

 logical studies by systematically examining a large number of 

 mammalian eggs. In the %gg of the rabbit he noted the disap- 

 pearance of the germinal vesicle and the formation of two polar 

 bodies as essential maturation phenomena, and after an exhaustive 

 investigation of fertilization processes, in the course of which he 

 saw spermatozoa with their heads in the surface of the Q^g.^ he 

 came to the conclusion that fertilization consisted of the minolincr 

 of the substance of the spermatozoon with the outer layer of cyto- 

 plasm. This statement is surprising in view of the fact that van 

 Beneden observed both the male and the female pronucleus, their 

 conjugation, and the cleavage nucleus, as well as numerous cleavage 

 stages. 



Hensen ('76) confirmed Bischoff's observation that in rabbits and 

 guinea-pigs the animals are in heat immediately after parturition, 

 but he found that ovulation does not always take place at this time. 

 He saw living spermatozoa, and witnessed their passage through 

 the zona pellucida. 



In ISTO, three investigators, Benecke, Eimer and Fries, published 

 papers on the eggs of bats. They each found living spermatozoa 

 in the uterus, and in some cases also in the Fallopian tube, while 

 the animals were hibernating ; but Benecke claimed that ovulation 

 and fertiliziition take place in the S2)ring of the year. After study- 

 ing the eggs of certain bats, however, van Beneden and Julin ('80) 



I 

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