BIOLOGY IN ITS WIDER ASPECTS 1273 



and that was in consonance with Spencer's theory. But this argu- 

 ment requires physiological and experimental vindication. 



If there he not this direct physiological connection between individua- 

 tion and rate of multiplication, 7c>hat is the cause of the differential 

 fertility ? The causes are no doubt multiple. It surely depends, in 

 part, on the conditions of housing, for in many of the working- 

 class houses there is a maximum of temptation and a maximum of 

 opportunity for sex gratification. And then among the poorer folk 

 and the more hard-pressed as regards physical work, there often 

 tends to be, on the whole, a restriction of human interests, and 

 therefore a tendency to become preoccupied with the things of 

 flesh. Possibly, though one must walk carefully here, there is in 

 many of the humbler folk a lack of the control factor, not that this 

 deficiency is not marked enough elsewhere. Very important is the 

 tradition of women's freedom and a realisation of the wisdom of 

 giving them a full life, and it may be that this idea is less current 

 among the working folk than among the better educated. Many 

 factors such as these have tended to bring about differential fertility, 

 but one must carefully notice that high fertility in itself is not to 

 be regarded as an indication of social or intellectual inferiority. 



Why should we he afraid of this differential fertility ? Because, 

 according to Pearson, 25 per cent, of the present generation beget 

 50 per cent, of the next. And if -a large fraction of that 25 per cent, 

 consists of types who are rather towards inferiority, then so much 

 the worse for the next generation. On the other hand, suppose one 

 can discount the lowest 10 per cent., for the reason that mortality 

 is very great amongst them, and suppose one can discount the 

 uppermost 10 per cent, who multiply very slowly, one would be 

 left with So per cent., who, after all, do not differ very much amongst 

 themselves in physique and mental ability. On the whole, it is the 

 mediocre folk who are carrying on the world's work, mediocre but 

 yet sound and fresh, and therefore we must not be unduly afraid 

 of the differential birth rate as long as we can rely on a fairly sound 

 80 per cent., or perhaps it should be 75 per cent., from whom, if we 

 read history aright, geniuses and artists have mostly come. 



Why did the hirth rate so extraordinarily rise and fall in British 

 history ? In the nineteenth century the population of England and 

 Wales was more than trebled — one of the biggest biological facts 

 that we know. The population of England and Wales in 1801 was 

 8,893,000; in 1901 it was 32,528,000 adults; it had more than trebled 

 during the century. W^hy was that? Because of the great increase 

 in material prosperity, which tends to lessen man's grip and to 

 lessen his restraints. But while a great many people during that 

 period of industrial prosperity were enjoying material well-being 

 to an extent previously unprecedented, there were under this what 

 Havelock Ellis calls "circles of Hell", where the proletariat were 



