116 The Development Theory: A Review. 



at first among many such obstacles, but one by one they have 

 been removed, and we may reasonably anticipate the same result 

 in the case of the theory of Organic Evolution. 



" Natural Selection " forms the topic of the fourth chapter. 

 This doctrine, called by Herbert Spencer the " survival of the 

 fittest," determines which among the numerous varieties pro- 

 duced by environment shall live aud which shall die. As the 

 Spartan council inspected each new-born infant, and decided 

 whether it should be reared as a citizen-soldier of the state or 

 exposed on Mount Taygetus to die of starvation, so natural 

 selection sits in judgment over every nurseling, and according 

 to circumstances pronounces its doom. If in harmony with its 

 surroundings, it may live ; if in discord, it mu>t die. If more 

 suited to its environment than its ancestors, it may even multiply 

 and crowd them out of existence. " Variation," says Prof. 

 Asa Gray, " is the wind, but natural selection is the rudder that 

 guides the organism." The mode in which natural selection acts 

 in thus directing the future form of the organism, is well illus- 

 trated by the authors with numerous and obvious examples. 



In connection with this important branch of the subject we 

 may remark that human selection is now in many cases far 

 more influential than natural selection, in determining the 

 survival of varieties. But the principles of hum;m selection are 

 often very different from those of nature apart from man. 

 Nature preserves only those most fit to take care of themselves 

 in the struggle for existence. Man often preserves those who 

 would have no chance in such a warfare. The weak in mind 

 or body, whom nature and Sparta would have condemned to 

 speedy death, are kept alive ; sentiment forbids their abandon- 

 ment to their natural fate. The wisdom of this policy is 

 sometimes called in question by sanitarians, but, whether wise or 

 unwise, it is established beyond overthrow. Beyond doubt the 

 prevailing practice tends to entail a terrible burden on our 

 civilization. Prof. A. M. Bell has recently called attention to 

 the danger of creating a race of deaf-mutes, by the constant 

 preservation and perpetuation of such persons. It is however 

 too wide a subject to be here discussed, and leads to other 

 and greater problems with which future sanitarians and legisla- 

 tors must .deal. If the sympathies of man will not allow the 



