CAUSATION OF SEX 213 



The older hypotheses were based upon various assumptions, 

 or upon limited evidence, and were born of a preconceived belief 

 that the influence of the environment was practically all-powerful 

 in the determination of Sex, as well as of other characters. The 

 influence of warmth, of geographical elevation, of quality and 

 quantity of food, of the relative age of parents, the freshness or 

 staleness of the germ-cells at the time of fertilisation, the social 

 rank and habits of the parents, the relative constitutional vigour 

 or sexual ardentcy of the father and mother, the number of 

 spermatozoa taking part in conception, and other factors, have 

 all been pressed into ser^dce in the attempt to explain the deter- 

 mination of Sex. But in this, as in other biological problems, 

 the day of the environmental dominancy is coming to its end. 

 It is becoming more clearly recognised that an organism is pre- 

 destined in its structure and its habits, for these latter are but 

 the manifestations of the hidden factors contained in the fertilised 

 egg-cell out of which the organism arises. 



Dr. Rumley Dawson's theory is in harmony with modern 

 investigation in so far as he ascribes the determination of Sex 

 to the inherent nature and structure of the egg- cells. But he 

 departs from our modern conceptions in that he affirms the 

 impotence of the male sex-cell to determine Sex at all. He 

 says : "It will come as a serious blow to the vanity of man to 

 know that this question must be answered with a decided nega- 

 tive. Man, or the male, has nothing to do with the causation of 

 the sex of the future child." He supports this conclusion by 

 adducing evidence which shows that certain women have 

 had only sons or daughters by different husbands, and that 

 certain female animals have had offspring all of one sex by several 

 different males. This evidence is certainly suggestive, but it is 

 hardly comprehensive enough to render it conclusive. On the 

 other hand, recent Mendelian experiments* tend to show that 

 the male does influence the determination of sex. It may be 

 possible that in some cases his influence is uniformly in one direction, 

 and it may be the peculiar structure of the female egg which 

 differentiates in the determination of Sex. But that does not 

 justify us in asserting " that the male has nothing to do with 

 the causation of Sex." To take a familiar analogy from domestic 

 life. It may be true that the mere man has no influence at all 

 in determining whether his wife's new dress shall be pink or 

 green, or striped purple, green, and white. That may be decided 

 wholly by the peculiar temper of the lady. But we imagine that 

 the cheque book of the husband does influence the possibility 

 of the lady having the dress at all. In the absence of a cheque, 



* See Mr. C. C. Hurst's paper on " Mendelism and Sex," page 125 of this 

 Journal. 



