392 LAMARCK, HIS LIFE AND WORK 



merit ' of the organism undergoing modificj^tion ; 

 and thus a form of Lamarckianism, greatly modified 

 by recent scientific discoveries, seems to meet most 

 of the difiSculties which arise in accounting for the 

 origination of species and higher groups of organ- 

 isms. Certainly ' natural selection ' or the ' sur- 

 vival of the fittest ' is not a vera causa, though the 

 ' struggle for existence ' may show us the causes 

 which have led to the preservation of species, while 

 changes in the environment of the organism may 

 satisfactorily account for the original tendency to 

 variation assumed by Mr. Darwin as the starting- 

 point where natural selection begins to act." 



In our work on The Cave Animals of North Amer- 

 ica,'^' after stating that Darwin in his Origin of 

 Species attributed the loss of eyes " wholly to dis- 

 use," remarking (p. 142) that after the more or less 

 perfect obliteration of the eyes, " natural selection 

 will often have effected other changes, such as an 

 increase in the length of the antennae or palpi, as a 

 compensation for blindness," we then summed up as 

 follows the causes of the production of cave faunas 

 in general: 



" I. Change in environment from light, even par- 

 tial, to twilight or total darkness, and involving 

 diminution of food, and compensation for the loss 

 of certain organs by the hypertrophy of others. 



" 2. Disuse of certain organs. 



" 3. Adaptation, enabling the more plastic forms 

 to survive and perpetuate their stock. 



"4. Isolation, preventing intercrossing with out- 



* Memoirs of the National Academy of Sciences, iv. , 188S, pp. 156; 

 27 plates. See also American Naturalist, Sept., 1888, xxii. , p. 808, 

 and Sept., 1894, xxviii., p. 333. 



