CAUSES OF DEGENERATION IN BLIND FISHES. 401 



in the shape of a continuous evolutionary process determined by inter- 

 nal causes, in the ease of which there can be no question whatever of 

 selection of persons or of a survival of the fittest — that is, of individuals 

 with the smallest rudiments. The gradual diminution continuing for 

 thousands and thousands of years and culminating in its final and ab- 

 solute effacement" can only be accomplished by germinal selection. 

 Germinal selection as applied to degeneration is the formal explanation 

 of Romanes' failure of heredity through the struggle of parts for food. 

 "Powerful determinants will absorb nutriment more rapidly than 

 weaker determinants. The latter, accordingly, will grow more slowly 

 and will produce weaker determinants than the former." If an organ 

 is rendered useless, the size of this organ is no longer an element in 

 personal selection. This alone would result in a slight degeneration. 

 Minus variations are, however, supposed to rest "on the weaker deter- 

 minants of the germ, such as absorb nutriment less powerfully than the 

 rest. This will enable the stronger determinants to deprive them even 

 of the full quantum of food corresponding to their weakened capacity of 

 assimilation, and their descendants will be weakened still more. Inas- 

 much, now, as no weeding out of the weaker determinants of the hind 

 leg [or eye] by personal selection takes place on our hypothesis, in- 

 evitably the average strength of this determinant must slowly but 

 constantly diminish — that is, the hind leg [or eye] must grow smaller 

 and smaller until it finally disappears altogether. . . . Panmixia 

 is the indispensable precondition of the whole process; for, owing to 

 the fact that persons with weak determinants are just as capable of life 

 as those with strong, . . . solely by this means is a further weak- 

 ening effected in the following generations." 



This theory presupposes the complex structure of the germ plasm 

 formulated by Weismann and rejected by various persons for various 

 reasons. But granting Weismann the necessary structure of the germ 

 plasm, can germinal selection accomplish what is claimed for it? I 

 think not. Granting that variations occur about a mean, would not 

 all the effects claimed for minus variations be counteracted I)y positive 

 variations? Eye determinants, which, on account of their strength, 

 secure more than their fair share of food, and thereby produce eyes 

 that are as far above the mean as the others are below, and leave de- 

 scendent determinants that are still stronger than their ancestry would 

 balance the effect produced by weak-eye determinants. It is evident 

 that a large, really extravagant development of the eye in such a fish 

 as Chologaster would not effect the removal of the individual by per- 

 sonal selection; still less so in Amblyopsis, which not only lives in com- 

 parative abundance, but has lived for twenty months in confinement 

 without visible food, and in which the eye is minute. It seems that all 

 the admitted objections to degeneration by panmixia apply with equal 



VOL. LVII.— 26 



