402 POPULAR SCIENCE MONTHLY. 



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. All its suppositions are found 

 to be but a house of cards when the actual conditions of degeneration 

 are considered. 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 pan- 

 mixia; 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 degen- 

 erate when they become useless'* finds no basis in fact, and is an example 

 of the inexact utterances abundant in the discussion of degeneration on 

 which it is entirely unsafe to build lofty theoretical structures. As one 

 example of the unequal degeneration we need only call attention to the 

 scleral cartilages and the rest of the eye of Troglichthys rosse. 



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 extensive degeneration. All are agreed 

 that the important point is degeneration beyond the point reached by 

 panmixia, the establishment of the degenerating process, whatever it 

 may be, in the germ, or, in other words, the breaking of the power of 

 heredity. It. is in the explanation of the latter that important differ- 

 ences of opinion exist. 



Weismann attempts to explain the degeneration beyond the point 

 which panmixia can reach by a process which not only is insufficient, 

 even if all his premises are granted, to produce the desired result with- 

 out the help of use transmission, but has as its result a horizontal degen- 

 eration which has no existence in fact. 



Eomanes supposed degeneration, beyond the point which may be 

 reached by panmixia, to be the result of personal selection and the fail- 

 ure of the hereditary force. The former is not applicable to the species 

 in question, and is denied by such an ardent Darwinist as Weismann 

 to be applicable at all in accounting for degeneration. Moreover, the 

 process as explained by Eomanes would result in a horizontal degenera- 

 tion which has no existence in fact. The second assumption, the failure 

 of hereditary force, is not distinguishable, as Morgan has pointed out, 

 from the effect of use transmission. 



The struggle of parts in the organism has not affected the eye 

 through the lack of room, since the space formerly occupied by the eye 

 is now filled by fat and not by an actively functioning organ. It is not 



