EVOLUTION AND ITS CONSEQUENCES. 23 



the case of the higher organisms we have muscle, converting the 

 results of nutrition into muscle ; skin and nails making more skin, 

 etc. ; brain making more brain ; bone making more bone. 



The prime question is the cause of the location of growth- 

 force. Experiments on this point are greatly needed, and in their 

 absence it will be necessary to take a wide survey of facts. 



A given animal Organism can only convert a given amount of 

 force, and that capacity must remain uniform so long as the 

 machine or structure remains the same. If, however, an addition 

 to its work is developed in one quarter, a subtraction from some 

 other region must take place if the whole amount remain the same. 

 When, then, a useful organ is added, subtraction from some less 

 important locality must result, and, as a consequence, the latter 

 must become still less prominent in the general economy. Hence, 

 the development of the useful class of organs already cited must 

 always be accompanied by a corresponding disappearance of use- 

 less ones. This would be by reduction or retardation. But, in 

 the case of the complex folds of the margins of the septa in the 

 ammonite, useless parts are added by acceleration. Here a gradual 

 increase in the amount of growth-force must be believed in. 



The representation of simple growth-force, i. e., the result of 

 bathmism, not specially located, is seen in general addition to size. 

 In domestication careful feeding, associated with protection against 

 all exhausting exposure or exertion, tends to this increase of size. 

 This is well known to be the case in hogs and cattle and animals 

 of quiet and easy life. The reverse conditions, as poor food, ex- 

 posure, and disproportionate exertion, reduce the size ; witness the 

 Maryland breed of cattle, and the semi-wild hogs of the Southern 

 States. This matter is, however, nicely balanced with the pro- 

 duction of motion, for if the latter be excessive, or the supply of 

 material for consumption be insufiBcient, growth-force must be 

 evolved in less amount. 



It will be necessary here to state that the supply for the con- 

 version of all the forces of the body is derived from the nutriment 

 as circulated in the blood. 



But the condition of plethora of growth-force is also the one 

 highly favorable for the appearance of variations of structure, or 

 the location of growth-force in new places. Domesticated animals 

 are notorious for this variation, while the still more numerous ex- 

 amples of *^ protean" species in nature are always predominant 

 forms, abundant in individuals and widely spread. For example. 



