MAMMALS 6 1 



the fishes. In their case Nature has chosen the first 

 method. The ova, which cannot save themselves fi-om 

 accident, are poured into the water, where fate decides 

 whether any of them will ever reach maturity ; moreover, 

 the little fishes that issue from them are exposed to all 

 sorts of dangers at a time when the young mammals are 

 safe inside the mother's womb. Hence the fishes must 

 produce enormous quantities of eggs. But the result is 

 the same in the long run. Both the mammals and the 

 fishes have the power of maintaining their kind. 



But when the maintenance of the species is secured 

 in the case of the mammals by reducing the chances of 

 destruction, the first method is excluded for them. The 

 fishes may mature large numbers of ova within their 

 bodies, but only on the understanding that the eggs 

 are small. If each egg were to attain the size of a fish 

 inside the mother's body, the number of them would 

 have to be very much restricted. Imagine a mother- 

 hare with fifty young ones in her body ; though even 

 this number is insignificant in comparison with the fishes. 

 She would be entirely helpless, would immediately be 

 devoured, and the capacity of great fertility would die 

 with her. In particular, the young developing within 

 her need food, and this would have to be derived from 

 the blood of the mother, which is vitally necessary for 

 her own maintenance. Finally, the division of the food 

 amongst so many would mean less for each of the 

 young, and therefore a weaker constitution ; they would 

 be destroyed at once, and thus again the disposition 

 to high fertility would perish. Think, for instance, 

 of human twins, or of triplets. If such children were 



