50 THE EVOLUTION O^ SEX. 



ovum, compared with one less favourably conditioned, in every 

 probability will tend to a female rather than to a male develop- 

 ment. Fertilisation, when the ovum is fresh and vigorous, 

 before waste has begun to set in, will corroborate the same 

 tendency. 



(c) Then if we accept Sutton's opinion as to a transitory 

 hermaphrodite period in most animals, from which the transition 

 to unisexuality is effected by the hypertrophy of the female side 

 or preponderance of the male in respective cases, the vast 

 importance of early environmental influences must be allowed. 

 The longer the period of sexual indifference (though this term 

 be an objectionable 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 pro- 

 duction of females, the reverse increase the probability of male 

 preponderance. 



The general conclusion, then, more or less clearly grasped 

 by numerous investigators, is that favourable nutritive con- 

 ditions tend to produce females, and unfavourable conditions 

 males. 



§ 4. Let us express this, however, in more precise language. 

 Such conditions as deficient or abnormal food, high temperature, 

 deficient light, moisture, and the like, are obviously such as 

 would tend to induce a preponderance of waste over repair, — 

 a katabolic 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 an 

 a?iabolic habit, and these conditions result in the production of 

 fonales. With some element of uncertainty, we may also 

 include the influence of the age and physiological prime of 

 either sex, and of the period of fertihsation. But the general 

 conclusion is tolerably secure, — that in the determination of 

 sex, influences inducing katabolism tend to result in production 

 of males, as those favouring anabolism similarly increase the 

 probability of females. 



^ 5. This is not all, however; the above conclusion is indeed 

 valuable, but it acquires a deeper significance when we take it 

 in connection with the result of a previous chapter. There it 

 was seen, as the conclusion of an independent induction, that 

 the males were forms of smaller size, more active habit, higher 



