Consideration of Weismann's Arguments 185 



alone sufficient to produce in some instances extraor- 

 dinarily complicated formations down to the most minute 

 peculiarities. The example of Kallima, a well known 

 leaf-like butterfly, will at once occur to every one. Never- 

 theless it is known that certain Lamarckians have had 

 the hardihood to wish to attribute these very perfect 

 resemblances to former, voluntary, chromoblastic, mime- 

 tic changes which do not now exist in the animal but 

 which can be demonstrated even now in certain other 

 animals, for instance in some fishes. The absence of 

 change in the object taken as a model which was imitated 

 only voluntarily at first, has resulted in the gradual with- 

 drawal of the imitative color mechanism from the con- 

 trol of the animal's will. 146 Here it is sufficient to 

 remark that the last word has certainly not yet been said 

 upon this voluntary mimicry which rightly excites the 

 greatest interest. In any case such imitative formations 

 as that of Kallima cannot be disposed of by simply refer- 

 ring them to natural selection alone, seeing that their 

 protective utility can commence to be manifested only 

 after they have attained an advanced degree of perfection. 

 "A muscle," insists Weismann, "can become greater 

 by use, but a claw, a bristle border, a dentition, a pro- 

 tuberance at an articulation, cannot become thicker, 

 longer or stronger by usage, it can only be used up." 147 

 But does not the very use of these inactiv.e parts dr, 

 better, the transmission through the inert substance to 

 the living substance of the mechanical action constituted 

 by this repeated use, provoke the living tissue to secrete 

 in larger quantity the chitinous substance of the bristles 

 and of the claws? 



l *'Le Dantec : Lamarckiens et Darwinians. P. 142 145. 

 147 Weismann : Neue Gedanken zur Vererbungsfrage. P. 65. 



