60 Animal Life and Intelligence. 



On the whole, we may say that there is some evidence 

 to show that in certain cases favourable conditions of 

 temperature, and especially nutrition, tend to increase the 

 number of females. We have seen that many animals 

 pass through a stage where the reproductive organs are not 

 yet differentiated into male and female, while in some there 

 is a temporary stage where the outer parts of the organ 

 produce ova and the inner parts sperms. We have also 

 seen that the ova are cells where storage is in excess ; the 

 sperms are cells in which fission is in excess. Favourable 

 nutritive conditions may, therefore, not incomprehensibly 

 lead to the formation of well-stored ova ; unfavourable 

 nutritive conditions, on the other hand, to the formation of 

 highly subdivided sperms. By correlated variation,* the 

 ova-bearing or sperm-bearing individuals then develop into 

 the often widely different males and females. 



* We have seen that when volume tends to outrun surface, fission may 

 take place, whereby the same volume has increased surface. But in un- 

 favourable nutritive conditions, the same surface which had before been 

 sufficient for nutrition may become, under the less favourable circumstances, 

 insufficient, and fission may again take place to give a larger absorbent sur- 

 face. Hence, possibly, the connection between insufficient nutriment and 

 highly subdivided sperms. 



