GENEOLOGICAL. 393 



sexual indifference (though, this term be an objec- 

 tionable one) continues, the more important must 

 be those outside factors, whether directly operative 

 or indirectly through the parent. Here again, then, 

 favourable conditions of nutrition, temperature, and 

 the like, tend towards the production of females, 

 the reverse increase the probability of male prepon- 

 derance. 



The general conclusion, then, more or less clearly 

 grasped by numerous investigators, is that favour- 

 able nutritive conditions tend to produce females, 

 and unfavourable conditions males. 



"Let us express this, however, in more precise lan- 

 guage. Such conditions as deficient or abnormal food, 

 high temperature, deficient light, moisture, and the 

 like, are such as tend to induce a preponderance of 

 waste over repair a relatively katabatic habit of body, 

 and these conditions tend to result in the production 

 of males. Similarly, the opposed set of factors, such 

 as abundant and rich nutrition, abundant light and 

 moisture, favour constructive processes, i. e., make for 

 a relatively anabolic habit, and these conditions tend 

 to result in the production of females. With some ele- 

 ment of uncertainty, we may also include the influence 

 of the age and physiological prime of either sex, and of 

 the period of fertilisation. But the general conclusion 

 is tolerably secure, that in the determination of sex, 

 influences inducing a relative predominance of kata- 

 bolism tend to result in production of males, as those 

 favouring a relative predominance of anabolism simi- 

 larly increase the probability of females." * 



(&) Other Experiments. (1) The importance 

 of the age or staleness of the germ-cells in affecting 

 the growth of the embryo has been carefully studied 



* Evolution of Bex, 4th ed., 1901, p. 55. 



