MULTIPLICATION OF THE HUMAN RACE. 485 



nutrition, we may suspect that it is in part due to greater 

 muscular expenditure. A kindred fact, admitting of a 

 kindred interpretation, may be added. Though the com- 

 paratively-low rate of increase in France is attributed to 

 other causes, yet, very possibly, one of its causes is the greater 

 proportion of hard work entailed on French women, by the 

 excessive abstraction of men for non-productive occupations, 

 military and civil. The higher rate of multiplication in 

 England than in continental countries general^, is not im- 

 probably furthered by the easier lives which English women 

 lead. 



That absolute or relative infertility is generally pro- 

 duced in women by mental labour carried to excess, is more 

 clearly shown. Though the regimen of upper-class girls is 

 not what it should be, yet, considering that their feeding is 



tenance of species. He argnes that the plethoric state of the individuals con- 

 stituting any race of organisms, presupposes conditions so favourable to life 

 that the race can he in no danger; and that rapidity of multiplication becomes 

 needless. Conversely, he argues that a deplethoric state implies unfavourable 

 conditions implies, consequently, unusual mortality; that is implies a 

 necessity for increased fertility to prevent the race from dying out. It may 

 be readily shown, however, that such an arrangement would be the reverse of 

 self-adjusting. Suppose a species, too numerous for its food, to be in the 

 resulting deplethoric state. It will, according to Mr. Doubleday, become 

 unusually fertile ; and the next generation will be more numerous rather than 

 less numerous. For, by the hypothesis, the unusual fertility due to the 

 deplethoric state, is the cause of undue increase of population. But if the 

 next generation is more numerous while the supply of food has remained 

 the same, or rather has decreased under the keener competition for it, 

 then this next generation will be in a still more deplethoric state, and 

 will be still more fertile. Thus there will go on an ever-increasing rate 

 of multiplication, and an ever-decreasing supply of food, until the species 

 disappears. Suppose, ou the ether hand, the members of a species to be in 

 an unusually plethoric siato. Their rate of multiplication, ordinarily suffi- 

 cient to maintain their numbers, will become insufficient to maintain their 

 numbers. In the next generation, therefore, there will be fewer to eat the 

 already abundant food, which, becoming relatively still more abundant, will 

 render the fewer members of the species still more plethoric, and still les 

 fertile, than their parents. And the actions and reactions continuing, tb* 

 species will presently die out from absolute barrenness. 



