560 THE EVOLUTION OP LIFE. 



many who recognize the inheritance of functionally-produced 

 changes, there are a few, like the Eev. Prof. Henslow, who 

 regard it as the sole factor. 



The foregoing chapters imply that the beliefs of neither 

 extreme are here adopted. Agreeing with Mr. Darwin that 

 both factors have been operative, I hold that the inheritance 

 of functionally-caused alterations has played a larger part 

 than he admitted even at the close of his life; and that, 

 coming more to the front as evolution has advanced, it has 

 pla3^ed the chief part in producing the highest types. I am 

 not now about to discuss afresh these questions, but to deal 

 with certain further questions. 



For while there has been taking place in the biological 

 world the major differentiation above indicated, there have 

 been taking place certain minor differentiations — there have 

 been arising special views respecting the process of organic 

 evolution. Concerning each of these it is needful to say 

 something. 



§ 1746. Among the implied controversies the most con- 

 spicuous one has concerned the alleged process called by 

 Prof. Weismann Panmixia — a process which Dr. Eomanes 

 had foreshadowed under the name of "the Cessation of 

 Selection." Dr. Eomanes says : — " At that time it appeared 

 to me, as it now appears to Weismann, entirely to supersede 

 the necessity of supposing that the effect of disuse is ever 

 inherited in any degree at all." * The alleged mode of action 

 is exemplified by Prof. Weismann as follows: — 



"A goose or a duck must possess strong powers of flight in the 

 natural state, but such powers are no longer necessary for obtaining 

 food when it is brought into the poultry-yard, so that a rigid selection 

 of individuals with well-developed wings, at once ceases among its 

 descendants. Hence in the course of generations, a deterioration of 

 the organs of flight must necessarily ensue, and the other members 

 and organs of the bird will be similarly affected." f 



* Darioin and after Darwin^ Part TI, p. 99. 

 f Essays upon Heredity, vol. i, p. t'O. 



