Consideration of Weismanris Arguments 181 



in hard substance, exactly as the skin of the sheep reacts 

 by the secretion of wool? There is nothing to prevent 

 such secretions, produced through functional adaptations, 

 serving later as protective shields and thus becoming 

 useful to the species in still another way. 



On the other hand the envelopes into which the 

 crustaceans and insects cited by Weismann insert one 

 part of their body might preserve the external surface 

 of that part from the hardening action of external agents, 

 just as houses and clothes may have contributed to the 

 disappearance of the hair in man. For one should not 

 consider the passive function of the hair or of the chiti- 

 nous substance so much as the active function of the * 

 tissues which secrete these substances; and this function 

 is essentially active for it is a specific reaction to external 

 influences. 



In this respect the hermit crab constitutes one of the 

 most conclusive proofs of the Lamarckian theory. For 

 this crab which is accustomed to insert the hinder part 

 of his body into empty snail shells has completely adapted 

 itself to the conformation of its new habitation, and this 

 bodily adaptation acquired by it has become hereditary 

 so that it is present in advance before the animal inserts 

 itself into its house. According to Weismann's view, 

 the animal must have first adopted the habit and natural 

 selection must have been able to exert its influence only 

 subsequently. Clearly both processes must go on at the 

 same time, the residence in the new habitation and the 

 adaptation to it; and the fact that these exist together 

 can be explained only through functional adaptation and - 

 inheritance of its effects. 143 



" 8 G. Cattaneo: I fattori della evoluzione biologica. P. 43 45; 



