OTHER THEORIES OF SPECIES-FORMING. 193 



that this eye degeneration was inherited by their young, 

 whose eyes, already bad, suffered further degeneration in 

 their life-time through disuse, and that after comparatively 

 few generations this cumulative actual morphologic degen- 

 eration through disuse and we know that unused active 

 organs, as muscles, stimulus-perceiving parts, etc., do actu- 

 ally degenerate in an individual's life-time through disuse 

 would reduce the eyes to a very degenerate condition. Other 

 cases of degeneration, especially of passive organs (i. e., 

 where the organ's condition was not so wholly a function 

 of use or disuse, but of the direct moulding influence of 

 extrinsic influences), are explained by Lamarckism on the 

 basis of the inheritance of the results of the direct action 

 or influence of environment on the organ. For example, 

 the gradual disappearance of pigment (blanching) charac- 

 teristic of many cave animals, would be explained by the 

 absence of the extrinsic factor, light, which is necessary to 

 stimulate pigment production. 



In necessarily closing this all too brief reference 3 to 

 panmixia, it may be said that Weismann himself has in 

 recent years recognised its unconvincing character ; and that 

 Plate, a strong upholder of selection, in a most careful 

 weighing of panmixia, finds it capable of explaining func- 

 tional degeneration but not any actual considerable mor- 

 phological rudimentation. 



The Theory of Germinal Selection was proposed by Weis- 

 mann in 1895, more definitively in 1896. Plate introduces 



discussion of this theor as follows : "Its 



Weismann's 



theory of ger- aim is the rehabilitation of the selection princi- 

 minal selection, < T , t1 .. , . 111, 



pie. It shall overcome all objections and doubts 

 which have been raised against the selection theory and shall 

 act as the magician's wand to clear all difficulties from its 

 way. Its strength shall avail in four directions. First, it 

 shall explain how not only degeneration (physiological) but 

 rudimentation (morphological) occurs in panmixia; second, 



