434 THE WONDER OF LIFE 



whose unlaid eggs form the delicacy known as caviare, 

 liberates more than a million. There may be 100,000 sperma - 

 tozoa in a cubic miUimetre. Many female butterflies die 

 after oviposition, and the same is true even of robust 

 animals like lampreys. The drone who succeeds in fertihzing 

 the queen hive-bee dies as he succeeds ; all the others, who 

 are unsuccessful, also die. A male spider often lays his hf e 

 on the altar of sex, and the same is true of some scorpions. 

 Viviparity is costly to the female, especially in Mammals ; 

 parturition is often exhausting ; feeding the young is a 

 drain on the mother's resources. 



In a very interesting essay, L'Espece et son serviteur 

 (Paris, 1913), Professor Cresson has illustrated the degree 

 to which the individual is subordinated to the weHare of 

 the species. Apart from the physiological sacrifice alluded 

 to, there is the energy expended in securing the safety of 

 the eggs, and in providing nourishment for the young. 

 In many insects, such as sand- wasps and scarabees, the 

 amount of work done for the welfare of the progeny is very 

 great. The non-existent offspring act, Cresson somewhat 

 fancifully suggests, as ' moral parasites ' on their parents. 



There is fatigue in nest-making, risk in incubation, 

 and both in attending to the nourishment, health, and 

 education of the young. Especially the mothers are, so to 

 speak, exploited. Nature taking advantage of their capacity 

 for seK-forgetfulness. Less metaphorically, it is their 

 meat and drink to spend themselves for the race. In the 

 case of social insects, the subordination of the single Ufe 

 is extraordinary, sometimes almost pathological. Cresson, 

 indeed, suggests the formula, ' Everything for the species ; 

 everything by the individual ; nothing for the individual '. 



Ageing and Senescence. — ^In most animals, as we 



