Consideration of Weismann’s 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.*** 
1448G_ Cattaneo: I fattori della evoluzione biologica. P. 43—45; 
