MULTIPLICATION OF THE RFMAX RACE. 4S5 



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

 muscular expeuditure. A kindred fact, adniittiug of a 

 kindred interpretation, may be added. Though the cora- 

 paratively-low rate of increase in France is attributed to 

 other causes, yet, ver}^ possibly, one of its causes is the greater 

 ]jroportion of hard work entailed on French women, by the 

 excessive ab>itraction of men for non-productive occupations, 

 militaiy and civil. The higher rate of multiplication in 

 England than in continental countries generally, is not im- 

 l)rnbably 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 argues that the plethoric stare of the individuals con- 

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

 that the race can be 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 tho 

 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 state. Their rate of multiplication, ordinarily suffi- 

 cient to maintain their numbers, will become insuflBcient 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 less 

 f'jrtile, than their parents. And tlie actions and reactiou3 continuing, tha 

 species will presently die out frofn absolute barrv<^nn*'ss. 



