328 BIOLOGY 



CONFORMITY TO TYPE 



Nothing is more marvelous, and at the same time more 

 evident, than the fact that the individuals of generation after 

 generation resemble each other so closely. Not only in general 

 features, such as the .structure of the body, the presence of 

 the proper number of legs, arms, etc., does the child resemble 

 the parent, but in an infinite number of details, in the color 

 of the eyes, the color of the hair, and even in many obscure 

 traits. The child may inherit from its parents the tendency 

 to become bald-headed at a certain age, or at a certain time in 

 life to put on a large amount of fat, etc. Through an endless 

 series of details, the child has a tendency to repeat its parents' 

 characteristics. 



Since scientists have begun to study life phenomena, they 

 have always puzzled over these marvelous facts, and have 

 advanced many speculations and theories to explain the simi- 

 larity of the offspring to its parents. Some of these theories 

 have been ingenious, some have been plausible, but all have 

 been imaginative. For the last century, particularly, this sub- 

 ject has been a matter of speculation; but until about 1884 

 none of the various speculations had sufficient plausibility to 

 receive any general acceptance. 



In 1884 there appeared a little essay by August Weismann 

 entitled "On Heredity" which advanced a new suggestion for 

 the explanation of heredity. In some of its phases this new 

 theory had been antedated by the writings of Brooks in America 

 and Galton in England. Nevertheless, it did not appear in a 

 clear-cut form until Weismann's essay came out in 1884, and 

 the theory has been almost universally known as Weismann's 

 theory of heredity. From the time of its appearance, the ex- 

 planation commanded wide acceptance and extended discussion. 

 As year by year has passed, the theory has been more and more 

 substantiated by facts, until at the present time it has practi- 

 cally universal acceptance. While it cannot be claimed that 

 we have a complete explanation of heredity, it is beyond ques- 



