310 THE STRUCTURAL EVIDENCE OF EVOLUTION. 



vertebrates of the Permian period. This would require long dis- 

 cussion to render clear ; nevertheless, I venture to make the asser- 

 tion that this series of structures is the result of definite and dis- 

 tinct organic forces, directed to special ends. We have yet to get 

 at the conflicting forces which have produced the results we see. 

 Mechanical evolution will give us a good deal to do for some time 

 to come. Of course, if motion has had any effect in modifying 

 structure, it behooves us to investigate those conditions which 

 give origin to motion in animals. First in order come the sensi- 

 bilities of the animal, which we have traced to simple conscious- 

 ness ; and stimuli, upon notice of which he immediately begins to 

 move. The primary stimulus of all kinds of motion is necessarily 

 touch. If a stone falls upon the tail of some animal which has 

 a tail, he immediately gets out of that vicinity. If a jelly-fish 

 with a stinging apparatus runs across an eel which has no scales, 

 the eel promptly moves. External applications of unpleasant 

 bodies will always cause an animal to change his location. Then 

 he is constantly assaulted by the dire enemy of beasts, hunger, an 

 instinct which is evidently universal, to judge from the actions of 

 animals. This seems to have fashioned, in large part, all forms 

 of life from the least to the greatest, from the most unorganized to 

 the most complex. Each exercised itself for the purpose of fill- 

 ing its stomach with protoplasm. Then come the stimuli which 

 appeal to a sense allied to that of touch, changes of tempera- 

 ture. No animals like to be too cold or too hot ; and when the 

 temperature is disagreeable, the tendency is to go away from that 

 locality. Among primary instincts must be included that of re- 

 production. After that comes the sensation of resistance, or, 

 carried to a high degree, of anger : when an animal's interests are 

 interfered with, its movements restricted, the most energetic dis- 

 plays are prompted. So, you see, it is a matter of necessity that 

 mental phenomena lie at the back of evolution, provided always 

 that the connecting link of the argument — that motion has ever 

 affected structure — be true. That is a point which, of course, 

 admits of much discussion. I have placed myself on the affirm- 

 ative side of that question ; and, if I live long enough, I expect to 

 see it absolutely demonstrated. 



Of course the development of mind becomes possible under 

 such circumstances. It is not like a man lifting himself up by 

 his boots, which it would be were there no such thing as memory. 

 But with that memory which accumulates, which formulates, first 



