v DEGENERATION OF STAMENS 211 



With regard to the eye Weismann himself admits that its 

 action might be affected by want of exercise, " inasmuch as 

 the chemical changes which take place in the retina when 

 vision takes place must cease when the eye is no longer 

 exposed to light." " But," he says, " how could the stamen of 

 a flower be affected by the alternative, whether the pollen 

 which it bears reaches the stigma of another flower or not. 

 And yet we know that hermaphrodite flowers have in some 

 cases reverted to the original separation of the sexes, by the 

 atrophy of the stamens in one flower, of the pistil in the 

 others. Whether this particular case is to be explained by 

 the cessation of selection whether active natural selection 

 does not play a part in it is another question. But let us 

 follow it further. After the anthers in the evolution of the 

 species have atrophied and entirely disappeared, their stalks 

 persist, not rarely possessing considerable length and thick- 

 ness. Gradually, but very gradually, these also degenerate, 

 and we find them in many species still of considerable length, 

 in others already quite short, in others again completely 

 absent, and only occasionally appearing in a particular flower 

 as a reminiscence of their former general presence. The 

 filament of the anther is no longer used, but how could it be 

 thereby directly affected and caused to atrophy ? Its struct- 

 ure has remained the same, the sap circulates in it as before, 

 and flows into it as much as into the neighbouring petals 

 or the pistil From our standpoint the matter is easily 

 explained, for the mere filament of the stamen is perfectly 

 immaterial to the continued existence of the species of plant 

 in question ; natural selection therefore withdraws its hand 

 from the organ, and it gradually atrophies." 



Here also, in my view, it must be claimed that the 

 absence of external stimuli contributes to produce the effect 

 on the one hand, the absence of the stimulation of the 

 female organs of the hermaphrodite by the process of fertilisa- 



