president's address. — SECTION D. 259 



young animals referred to above is held to be sufficiently accounted for 

 by these facts. Whether this last conclusion is adopted or not it must 

 be admitted that, with this possible exception, there is no scrap of 

 evidence of foster-mother influence. 



Those of us that at first were troubled with no doubts on the 

 question of use inheritance remember how conclusive seemed the 

 argument that failure to use an organ led gradually to the want of 

 power to use it, and to its degeneration and ultimate disappearance ; 

 that the animals living in dark caverns came, in the course of many 

 generations, to lose their eye structure more or less completely as a 

 result of disuse. Eigemann (" Cave Vertebrates of America," Carnegie 

 institution, 1909), with an unrivalled knowledge of the American cave 

 fauna, still supports the view that disuse leads to modification that is 

 transmissible. The caverns became peopled in the first case, indeed, 

 " by animals predisposed to shun the light or creep under rocks or into 

 crevices " (Eigemann, "' The Eyes of Rhineura Floridana," Proc. of the 

 "Washington Academy of Sciences, Vol. IV., p. 535, 1902). There is, 

 therefore, at the outset a suggestion of great value to those that deny 

 the heritable effects of disuse. Yet, after a careful examination of all 

 the evidence, and a review of the various theories that would seek to 

 explain it, Eigemann says, " The Lamarckian view, that through disuse 

 the organ is diminished during the life of the individual in part at least 

 on account of the diminution of the amount of blood going to a resting 

 organ, and that this effect is transmitted to succeeding generations, 

 n»t only would theoretically account for unlimited progressive degenera- 

 tion, but is the only view so far examined that does not on the face of 

 it present serious objections " (p. 240). Again, " Considering the parts 

 most affected, and the parts least affected, the degree of use is the only 

 cause capable of explaining the conditions. Those parts most active 

 during use are the ones reduced most, viz., the muscles, the retina, optic 

 nerve, and dioptric appliances — the lens and vitreous parts. Those 

 organs occupying a more passive position, the scleral cartilages, have 



been much less affected ; and the bony orbit least All 



indications point to use and disuse as the effective agent in moulding 

 the eye." 



The case of Amblyopsis, a genus of cave fishes, is a noticeable one. 

 The loss of pigment brought about by life for many generations in the 

 absence of light, has become heritable, and the young animals do not 

 become pigmented when reared in the light. 



Arthur M. Barita ("The Fauna of Mayfield's Cave, '* Carnegie 

 Institution, 1907) confirms Eigemann's views that cave animals have 

 often acquired heritable somatic modifications as the result of the 

 action of their special environment. 



Examples of the persistence of environmental influence in plants 

 are given by Kleb's in his essay on " The Influence of Environment on 



I 2 



