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1272 LIFE : OUTLINES OF GENERAL BIOLOGY 



splendidly healthy set of people on the whole, the number is 258 

 per 100 couples, and that is not unsatisfactory from the biological 

 point of view. But among general labourers the figure is 438 per 

 100 couples; the average family being thus over 4. Prof. Raymond 

 Pearl has collected some statistics for America, and though his 

 total numbers were small, his data were very accurate. He gives 

 thishttle table:— 



Families of farmers . . . . . . . . 5 -92 



Families of teachers and professors .. .. 4-89 



Families of merchants, doctors and lawyers . . 4-82 



The farmers' families showed an average of 5-92 children, while 

 teachers, with professors thrown in, had an average of 4*89 per 

 family. The average family of the general professional class, mer- 

 chants, doctors, lawyers. Congressmen, and the like, was 4*82 — 

 a more hopeful set of statistics than has sometimes been given for 

 the size of the family in North America. 



Why is there this differential fertility ? Llerbert Spencer gave an 

 interesting answer which is probably somewhat misleading. He said 

 there was a physiological nexus between individuation and the rate 

 of reproduction; that is to say, the more individuality, the more 

 culture, the more morality, the more mentality shown by the 

 individuals the less would be their rate of reproduction. The tape- 

 worm has 8,000,000 eggs, while the golden eagle never lays more 

 than two a year. The golden eagle has a very high individuality 

 with a low rate of reproduction; the tapeworm with its degenerate 

 body has an enormous rate of reproduction. And so with other 

 types. If we understand Spencer aright, he thought that there was 

 a direct physiological nexus between individuation and the rate of 

 reproduction. But what one sees in the animal kingdom may be 

 interpreted as follows : when a type of animal varied approximately 

 at the same time in two different directions, namely, (a) towards 

 increased cerebral capacity associated with increased parental care, 

 and (h) towards decreased or economised reproduction, then there 

 came about an adjustment towards small famihes. Thus birds 

 advanced greatly in the direction of intelligence, sympathy, and 

 parental care, and, having varied greatty in that direction, they were 

 able to afford to take advantage of a variation in economised 

 reproduction. 



There do not seem to be many facts to bear out the idea that 

 individual improvement in intelligence or education or morals will 

 have ipso facto any direct physiological effect on the fertility, though 

 this was one of the arguments used many years ago against the 

 higher education of women. It was said that heightened individua- 

 tion would reduce their fertility and cause decreased reproduction — • 



