PHYSIOGENESIS. 241 



tective resemblances will be found an account of sev- 

 eral examples of animals which have apparently ac- 

 quired a resemblance to their surroundings by the 

 transference of pigment to their bodies in their food. 



f. The Blindness of Cave- Animals. 



Neo-Lamarckian writers have always ascribed the 

 absence or rudimentary condition of the eyes charac- 

 teristic of animals which dwell exclusively in caves, to 

 disuse consequent on the absence of light. Lamarck 

 ascribed the rudimentary condition of the eyes in the 

 .mole to this cause. As the removal of so important 

 an organ as the eye is not accomplished in a single 

 generation, the element of heredity enters the propo- 

 sition. This subject is reserved for Part Third of this 

 book ; nevertheless, for the present suspending judg- 

 ment as to this question, it has been rendered exceed- 

 ingly probable by embryological investigations into the 

 history of dwellers in darkness, that the Neo-Lamarck- 

 ian view is the correct one. 1 Says Packard : 



' ' In my essay on The Cave Fauna of North America 

 (p. 139), I record the fact that in the young of the 

 blind crayfish {Orconectes pelluddus}, the eyes of the 

 young are perceptibly larger in proportion to the rest 

 of the body than in the adult, the young specimen ob- 

 served being about half an inch in length. Previously 

 to this, Dr. Tellkampf, in 1844, remarked that 'the 

 eyes are rudimentary in the adults, but are larger in 

 the young.' Mr. S. Garman states, regarding the blind 

 Cambarus of the Missouri Cave : 'Very young speci- 

 mens of C. setosus correspond better with the adults of 

 C. bartonii', their eyes are more prominent in these 



II am indebted for a resume of this subject to Packard, American Nat- 

 uralist, 1884, p. 735. 



