386 ANIMAL BIOLOGY 



practical aim of the science of Eugenics. At the present 

 time there are various agencies working toward the 

 deterioration of the inborn qualities of the race and others 

 which have the opposite tendency and the trend of our 

 biological development depends upon which set of ten- 

 dencies is the more potent. One very serious condition 

 which has come into existence largely during the last 

 half century is the diminishing size of the family among the 

 educated and successful classes. While there has been a 

 general decline in the birth rate in most civilized coun- 

 tries this decline does not affect all classes of society alike. 

 A decreasing birth rate is in itself no menace so long as it 

 is not so low as to cause, as in France, an actual decrease 

 of population. But when the defective classes and those 

 with inferior inheritance continue to produce many 

 children while the birth rate of those with superior endow- 

 ments becomes greatly reduced, a deterioration of the 

 hereditary qualities of the race will inevitably result. 



Seventy-five years ago the educated classes had as a 

 rule large families, but their birth rate has gradually 

 decreased until they average in the United States between 

 two and three children. The average number of children 

 of graduates of Yale and Harvard is scarcely over two per 

 family and the families of most other college graduates 

 are but little larger. It is much the same with successful 

 men of business and the higher classes of artizans. The 

 birth rate of foreign immigrants is much higher, the average 

 family in Massachusetts for instance having 4.7 children 

 while the families of the American born have only 2.7 

 children. It requires nearly four children per family to 

 replenish the population; many fail to marry or else die 

 before reaching maturity so that, starting with four, only 

 two (or a little over) take the places of their parents and 

 become producers of children. It follows that stocks with 



