The Theory of Natural Selection. 281 



arrangements, which might reasonably be supposed 

 due, like the phenomena of crystallization, to com- 

 paratively simple physical causes. On the contrary, 

 they everywhere and habitually exhibit so deep-laid, 

 so intricate, and often so remote an adaptation of 

 means to ends, that no machinery of human contrivance 

 can properly be said to equal their perfection from a 

 mechanical point of view. Therefore, without question, 

 the hypothesis which first of all they suggest or 

 suggest most readily is the hypothesis of design. 

 And this hypothesis becomes virtually the only hypo- 

 thesis possible, if it be assumed as it generally was 

 assumed by natural theologians of the past, that all 

 species of plants and animals were introduced into 

 the world suddenly. For it is quite inconceivable that 

 any known cause, other than intelligent design, could 

 be competent to turn out instantaneously any one of 

 these intricate pieces of machinery, already adapted 

 to the performance of its special function. But, on the 

 other hand, if there is any evidence to show that one 

 species becomes slowly transformed into another 

 or that one set of adaptations becomes slowly changed 

 into another set as changing circumstances require, 

 then it becomes quite possible to imagine that a 

 strictly natural causation may have had something 

 to do with the matter. And this suggestion becomes 

 greatly more probable when we discover, from geo- 

 logical evidence and embryological research, that in 

 the history both of races and of individuals the 



words as "contrivance," "purpose," &c., which are strictly applicable 

 only to the processes or the products of thought. But when it is under- 

 stood that they are used in a neutral or metaphorical sense, I cannot see 

 that any harm arises from their use. 



