54 MENDELISM AND 



an early stage in the segmentation of the ovum, 

 or only at a later stage of development, we know 

 that the gametes ultimately formed have descended 

 bv a series of cell-divisions from the fertilised ovum 

 or zygote cell from which development commenced. 

 If segregation takes place at the reduction divisions 

 we might suppose that half the gametes formed 

 are sperms and half are ova, and that in the male 

 the latter do not survive but perish and disappear. 

 But in this case it would be the whole of the chromo- 

 somes coming from the original female gamete 

 which would disap^Dear, and the spermatozoon 

 would be incapable of transmitting characters de- 

 rived from the female parent of the individual in 

 which the spermatozoa were formed. An individual 

 could never inherit character from its paternal 

 grandmother. This, of course, is contrary to the 

 results of ordinary Mendelian experiments, for 

 characters are inherited equally from individuals 

 of either sex, except secondary sexual characters 

 and sex-linked characters which we shall consider 

 later. 



Similarly, if we suppose that segregation of ovum 

 and sperm occurs in the female, the sperms must 

 disappear and the ovum would contain no factors 

 derived from the male parent. But the theory 

 sui)poses that the segregation of male and female 

 does occur in the female, that half the ova are female 

 and half are male. What meaning are we to attach 

 to the words ' male ovum ' or even ' male producing 

 ovum ' ? It is a fundamental principle of Mendelism 

 that the soma does not influence the gametocytes 

 or gametes; we have therefore only to consider 

 the sex of the gametes themselves, derived from a 



