body is formed. The body does not produce the germ 

 cells, but merely houses and nourishes them. 



During the formation of the body by the multiplica- 

 tion and differentiation of the body cells, the primary germ 

 cells are relatively inactive, but at maturity they become 

 active. By division spermatogonia and ogonia are formed, 

 then spermatocytes and oocytes, and finally spermatozoa and 

 ova (See Fig. 6). 



Chapter 7— HEREDITY AND INHERITANCE 



"Some are born great, — {Heredity). 

 Some achieve greatness, — {Function). 

 Some have greatness thrust upon them."^ — {Environment) . 



— Shakespeare. 



Heredity has been well defined as "the genetic relation 

 between successive generations," and inheritance, "all that 

 the organism is or has to begin with, in virtue of its heredit- 

 ary relation to parents and ancestors" {Thomson, Heredity) . 



The three factors that influence an organism are hered- 

 ty, function, and environment.^ 



The heredity factor is often called Nature, and 

 those of function and enviroment called Nurture. 



The modifications produced by nurture are not trans- 

 missible, but they may be re-impressed on each generation. 

 Every inheritance requires an appropriate nurture, if it is to 

 realize itself in development. Nurture supplies the libera- 

 ting stimuli necessary for the full expression of the inheri- 

 tance. "A man's character, as well as his physique, is a 

 function of nature and of nurture." 



The determination of the laws of heredity is, perhaps, 

 the most important of biological inquiries for the reason 

 that if they were fully understood the problem of the mode 

 of evolution of organic beings would be solved. But this 



(1) — Dr. Chalmers Mitchell, in a recent volume entitled "Evolution and 

 the War," discusses the factors operating in the making of 

 nationality, and states that "the study of nationality is really a 

 study of 'Kultur,' " i.e., the "whole set of forces, partly selective, 

 partly directive, political, educational, social, environmental that 

 go to" the moulding of the national character, everything in fact 

 that nurture can impose on plastic nature." He questions the 

 opinions of Dr. Starr Jordan ("The Human Harvest"), Dr. Saleeby 

 ("Parenthood and Race Culture"), Dr. J. A. Thomson and others 

 regarding the effect of war upon the human stock; and chatls 

 those eugenists who claim that by selective agencies m breeding 

 mental, moral and emotional qualities of a people can oe 

 modified. 



Dr. Mitchell contends that "nurture is inconceivably niore im- 

 portant than nature," and adduces many arguments in favor of 

 the contention (Chap. V.). 



45 



