296 



THE AMERICAN NATURALIST 



[Vol. LIV 



We have therefore in the ostrich certain hereditary 

 structural characters whose independent formation could 

 in every respect be accounted for during the life-time of 

 the bird from the known responsive nature of the skin 

 and the habits of the creature. Examination of the adult 

 alone and a knowledge of its activities would have jus- 

 tified us in regarding them as acquired adaptive charac- 

 ters, had not observation proved that they appear on the 

 chick prior to hatching, and before the parts could have 

 been subjected to the usual stimuli. The ostrich has 

 hereditary character* which could also be produced as 

 adaptive responses to the habits of the bird. 



The old contentious question therefore arises as to 

 whether the character first appeared as a response of the 

 skin to the habits of the ostrich and has now become 

 hereditary, or whether, having arisen fortuitously in the 

 germ plasm, wholly apart from any adaptive need of the 

 bird, it is now utilized by it. Has the habit developed the 

 character until it has become transmissible or, the char- 

 acter being given, has it permitted of the adoption of the 

 habit? The reply is simple and free from doubt: the cal- 

 losity under any circumstances would develop pari passu 

 with the habit and need of the bird, mid neither the cal- 

 losity nor the habit is dependent upon any antecedent 

 formation. If the character did not arise in the first in- 

 stance from the activities of the bird, subsequently be- 

 coming transmissible, it is maiii t'i'-t tli;it it could originate 

 by two distinct and independent methods, namely, from 

 the germ-plasm and from post-natal stimuli. 



It is not the first time that the presence of callosities 

 in the embryos of animals provided with them in the 

 adult has been adduced as evidence that characters orig- 

 inating during the life-time may be transmitted to the 

 offspring. The best known case is that of the wart-hog, 

 another African type— Ex Africa sew per aliqiiid uori. 

 With reference to this Professor J. Arthur Thomson 3 



