CAUSES OF DEGENERATION. 239 



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

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

 responding to their weakened capacity of assimilation and their descendants will 

 be weakened still more. Inasmuch now as no weeding out of the weaker deter- 

 minants of the hind leg (eye) by personal selection takes place on our hypothesis, 

 inevitably the average strength of this determinant must slowly but constantly 

 diminish, that is, the hind leg (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 weakening 

 effected in the following generations." 



This theory presupposes the complex structure of the germplasm formulated 

 by Weismann. But granting Weismann the necessary structure of the germplasm, 

 can germinal selection accomplish what is claimed for it? I think not. Grant- 

 ing that variation occurs about a mean, would not all the effects claimed for minus 

 variations be counteracted by positive variations? Eye determinants, that 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, may leave 

 descendent determinants that are still stronger than their ancestry. 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 personal selection, still less so in 

 Amblyopsis, which not only lives in comparative abundance, but has lived for 20 

 months in confinement without visible food. It seems that all the admitted objec- 

 tions to degeneration by panmixia apply with equal force to germinal selection. 

 This, however, would be changed were the effect of disuse admitted to affect the 

 determinants, and this it seems Weismann has unconsciously admitted. So far 

 we have considered germinal selection in the abstract only. In the concrete we 

 find that degeneration is not a horizontal process affecting all the parts of an organ 

 alike as Weismann presupposes, not even a process in the reverse order of phyletic 

 development, but the more vital, most worked parts degenerate first with disuse 

 and panmixia, the passive structures remain longest. The rate of degeneration 

 is proportional to the past activity of the parts and the statement that "passively 

 functioning parts, that is, parts which are not alterable during the individual life 

 by function, by the same laws also degenerate when they become useless" is not 

 applicable to the eyes. As one example of the unequal degeneration we need only 

 call attention to the scleral cartilages and the rest of the eye of Troglkhthys rosa} 



All are agreed that natural selection alone is insufficient to explain all, if any, 

 of the processes of degeneration. All either consciously or not admit the principle 

 of panmixia, and all are now agreed that this process alone can not produce exten- 

 sive degeneration. All are agreed that the important point is degeneration beyond 

 the point reached by panmixia, the establishment of the degenerating process, what- 

 ever it may be, in the germ, or in other words, breaking of the power of heredity. 

 It is in the explanation of the latter that important differences of opinion exist. 



1 I must again guard against cross-counter conclusions. In the Brotulida? the passive cartilages are among the 

 first things to go. 



