62 GERMINAL SELECTION. 



for example, in the simultaneous rise of instincts and 

 protective similarities, or in the harmonious and 

 simultaneous augmentation of two co-operant but in- 

 dependent organs, as of the eye and of the centre of 

 vision, or of the nerve and its muscle, etc. 



The "secret law/' of which Wolff prophetically 

 speaks in his criticism of selection, is in all likeli- 

 hood naught else than germinal selection. This it is 

 that brings it about that the necessary variations are 

 always present, that symmetrical parts, for example, 

 the two eyes, usually vary alike, but under circum- 

 stances may vary differently, for example, the two 

 visual halves of soles; that homodynamic parts, (for 

 instance, the member-pairs of Arthropoda,) have fre- 

 quently varied alike, and not infrequently and in con- 

 formity with the needs of the animal, have varied dif- 

 ferently. It brings it about also that conversely species 

 of quite different fundamental constitutions occasion- 

 ally vary alike, as instances of mimicry and numerous 

 other cases of convergence show us. As soon as utility 

 itself is supposed to exercise a determinative influence 

 on the direction of variation, we get an insight into 

 the entire process and into much else besides that has 

 hitherto been regarded as a stumbling-block to the 

 theory of selection, and which did indeed present diffi- 

 culties that for the moment were insuperable as, 

 for example, the like-directed variation of a large 

 number of already existing similar parts, seen in the 

 origin of feathers from the scales of reptiles. The 

 utility in the last-mentioned instance consisted, not in 

 the transformation of one or two, but of all the scales ; 

 consequently the line of variation of all the scales must 

 have been started simultaneously in the same direction. 

 A large part of the objections to the theory of selection 



