38 GERMINAL SELECTION. 



unmistakably to the conclusion that the displacement 

 of the zero-point of variation by personal selection is 

 not and cannot be the only factor in the determination 

 and accomplishment of the direction of variation. I 

 refer to retrogr essive developmen t, the gradual degen- 

 eration of parts or characters that have grown useless,' 

 the gradual disappearance of the eye in cave-animals, 

 of the legs in snakes and whales, of the wings in cer- 

 tain female butterflies, in short, to that entire enor- 

 mous mass of facts comprehended under the designa- 

 tion of "rudimentary organs." 



I have endeavored on a previous occasion to point 

 out the significance of the part played in the great 

 process of animate evolution by these retrogressive 

 growths, and I made at the time the statement that 

 "the phenomena of retrogressive growth enabled us in 

 a greater measure almost than those of progressive 

 growth to penetrate to the causes which produce the 

 transformations of animate nature." Although at that 

 time^ I had no inkling of certain processes which to- 

 day I shall seek to prove the existence of, yet my 

 statement receives a fresh confirmation from these 

 facts. 



For, in most retrogressive processes active selection 

 in Darwin's sense plays no part, and advocates of the 

 Lamarckian principle, as above remarked, have rightly 

 denied that active selection, that is, the selection of 

 individuals possessing the useless organ in its most 

 reduced state, is sufficient to explain the process of 

 degeneration. I, for my part, have never assumed this. 



^In 1886. See my paper on "Retrogression in Nature," 

 published in English in Nos. 105, 107, 108, and 109 of The 

 Open Court, and also in my essays on Heredity, Jena, 1892. 



