MENDELISM AND SEX 



155 



5 = female, and S = male. 



A theory must not be judged too severely upon 

 the basis of a few exceptions. Ovulation may have 

 been suspended or irregular, or other disturbing 

 causes may temporarily have disturbed the normal 

 sequence. And if a large number of families, taken 

 at random, in general confirm the theory, the excep- 

 tions to it must be regarded as exceptional. But 

 still there are certain theoretical objections to the 

 theory, into which we cannot now enter. Further 

 it appears that the author's assumption, that the 

 male does not influence the determination of sex, 

 is inconsistent with a number of facts. For, as we 

 have already seen (supra page 139), in some cases 

 the male is the arbiter of sex ; and, in all cases, 

 by virtue of his definite gametic composition, he 

 may be said to exercise as much influence as the 

 female in the determination of the sex of his offspring. 



If we now briefly summarise the facts and con- 

 ceptions which we have considered in detail, we 

 may say the evidence is clear that sex is pre- 

 destined in the germ-cells, and is determined at the 

 moment of fertilisation. It is highly probable, too, 



