134 Animal Life and Intelligence. 



hereafter. We may here notice, however, that at first 

 sight the hypothesis seems to prove too little or too much. 

 For while modifications of tissues, the effects of use and 

 disuse, are said to be inherited, the total removal of tissues 

 by amputation, even if repeated generation after generation, 

 as in the docking of the tails of dogs and horses, formerly 

 so common, does not have the effect of producing offspring 

 similarly modified. Professor Weismann has recently 

 amputated the tails of white mice so soon as they were 

 born, for a number of generations, but there is no curtail- 

 ment of this organ in the mice born of parents who had 

 not only themselves suffered in this way, but whose 

 parents, grandparents, and great-grandparents were all 

 rendered tailless. The pangenetic answer to this objection 

 is that gemmules multiply and are transmitted during 

 long series of generations. We have only to suppose that 

 the gemmules of distantly ancestral tails have been passing 

 through the mutilated mice in a dormant condition, await- 

 ing an opportunity to develop, and the constant reappear- 

 ance of tails is seen to be no real anomaly. In this case 

 the gemmules of the parental and grandparental tail are 

 simply absent. But if the muscles of the parental tail 

 were modified through unwonted use, the modified cells 

 would give rise to modified gemmules, which would unite 

 in generation with ancestral gemmules, and to a greater 

 or less degree modify them. The difference is between the 

 mere absence of gemmules and the presence of modified 

 gemmules. And the fact that it takes some generations 

 for the effects of use or disuse to become marked is 

 (pangenetically) due to the fact that it takes some time for 

 the modified gemmules to accumulate and be transmitted 

 in sufficient numbers to affect seriously the numerous 

 ancestral gemmules. 



The direction in which Professor W. K. Brooks has 

 recently sought to modify Darwin's pangenetic hypothesis 

 may here be briefly indicated. He holds that it is under 

 unwonted and abnormal conditions that the cells are 

 stimulated to produce gemmules, and that the sperm is 



