262 EVOLUTION OF TO-DAY. 



jection is even more forcibly urged against Mivart's 

 theory since these extraordinary births are more 

 difficult to understand than are simple variations. 

 The appeal to an internal law regulating them is no 

 explanation, but simply a method of avoiding the 

 question. 



Neo-Lamarckianism : Use and Effort. 



A theory more intelligible than the preceding, 

 and more logical, since it appeals to known rather 

 than unknown factors, is the old idea of Lamarck. 

 This theory finds in use and effort the active forces 

 causing the modification of animals. It is, perhaps, 

 the simplest explanation which has been offered. 

 Not only this, but it was the first suggestion. La- 

 marck, who first formulates a definite evolution 

 theory used this idea as its foundation. But the 

 theory did not find favor with Darwin, and it has, 

 consequently, received little support until within a 

 few years. It has of late, however, been taken up 

 by various American scientists, who, having made 

 some slight modifications, have ably supported it. 

 The theory as held to day has been called neo- 

 Lamarckianism, and may be regarded as the Ameri- 

 can school of evolution, since its chief supporters 

 belong to this continent. Its most prominent ad- 

 vocates are Cope and Hyatt. 



Neo-Lamarckianism finds the primal modifying 

 factor in the activities of animals in their endeavors 

 to meet the requirements of changing conditions. 

 Something is attributed to the direct action of 

 chemical and physical forces produced by changes 



