XXX11 THE SPECIES CONCEPTION. 



To the naturalist knowing these shells in the field, it would 

 seem absurd to claim that the colors are protective in any 

 ordinary sense, or that their evolution is controlled or directed 

 by any sort of selection. It is perfectly obvious that one 

 color or pattern is as good as another. A pattern predomin- 

 ating in one colony may be rare in the next, living under con- 

 ditions apparently the same, and perhaps not half a mile dis- 

 tant. White shells, the most conspicuous of all to my eye, 

 are as abundant as any others; though I would not give the 

 impression that any Achatinella is very conspicuous. Mr. 

 Perkins found no evidence that Achatinellidcz are ever eaten 

 by birds, or in fact by any animal but the imported rats 

 (Fauna Hawaiiensis I, vi, p. ccxxvi). 



Weissmann's treatment of the subject of specific differen- 

 tiation of Hawaiian snails does not appear to be based upon a 

 sufficient knowledge of the facts. He considers the pheno- 

 mena due to adaptive variation of species in a new environ- 

 ment. 1 



I have elsewhere expressed the opinion that the opaque 

 coloring everywhere characterizing land shells living in ex- 

 posed situations is an adaptation to exclude light. The 

 corneous yellow, or light brown tints usual in ground 

 snails are more translucent. The particular patterns evolved 

 since arboreal life was assumed do not seem to affect the 

 existence of the species. In common with Dr. Cooke and 

 other observers, I have been unable to trace any constant 

 relation between coloration and physical conditions (except 

 as noted below), and there is certainly no connection between 

 color and the species of tree inhabited. 



In the typical group of Achatinella (Apex], a certain cor- 

 relation seems to exist between the pattern and elevation, 

 banded forms occupying higher situations than streaked forms 

 of the same species, at least in many cases. I believe that 

 the relation is an indirect one. Banded patterns have been 

 evolved from streaked, as stated on p. xx; evolution in more 

 humid stations would naturally be more rapid than in lower, 



ir Phe Evolution Theory, translation by J. A. Thomson and Margaret K. 

 Thomson, London, 1904, II, 293-296. 



