248 Heredity. 



From the necessity for impregnation in most cases, it 

 lias been assumed that the essential function of the male 

 clement is to quicken the germ, and thus start the pro- 

 cess of development. It is true that it does have this 

 function in many cases; but comparative study shows 

 that the Qg^ itself is alive, and does not need quicken- 

 ing, and that this must be regarded as a secondary and 

 derived function of the male element, not the essential 

 and primitive function. 



That this is the case is shown by the fact that, while 

 the earlier stages in the developmental process are suf- 

 ficiently alike in different animals to admit of a compa- 

 rison between them, the stage at which impregnation 

 takes place is not fixed, but variable. In some cases the 

 ovarian Qgg remains without change until it is impreg- 

 nated; and the first step in the developmental process, 

 the disappearance of the germinative vesicle, is the im- 

 mediate result of the union of the spermatozoa with the 

 ovum. In other cases the germinative vesicle disap- 

 pears, and the Qgg then remains inactive until it is im- 

 pregnated; and this is followed at once by segmentation. 

 In other cases segmentation takes place without impreg- 

 nation. Other eggs develop still further; and, finally, 

 there are many animals whose unfertilized eggs not only 

 commence but complete the developmental process, and 

 give rise to adults which may in turn produce young in 

 the same wav: and this mav 2:0 on indefinitely, without 

 the intervention of a male. The queen bee is able to 

 lay fertilized or unfertilized eggs, and they are equally 

 alive and capable of development. 



These facts show conclusively that the essential func- 

 tion of the male element is not the vitalization of the 



germ. 



Turning now to another aspect of our subject, we find 



