306 THE CASE AGAINST EVOLUTION 



is an "effect of long-continued disuse," and to regard the phe- 

 nomenon as "wholly, or mainly, due to natural selection," e.g. 

 in the case of the wingless beetles of the island of Madeira. 

 "For during successive generations," he reasons, "each indi- 

 vidual beetle which flew least, either from its wings having 

 been ever so little less developed or from indolent habit, will 

 have had the best chance of surviving from not being blown 

 out to sea; and, on the other hand, those beetles which most 

 readily took to flight would oftenest have been blown to sea, 

 and thus destroyed." In a third class of instances, however, 

 he assigns the principal role to disuse, e.g. in the case of the 

 blind animals "which inhabit the caves of Carniola and Ken- 

 tucky, because," as he tells us, "it is difiicult to imagine that 

 eyes, though useless, could be injurious to animals living in 

 darkness." Hence he concludes that, as the obliteration of 

 eyes has no selection-value, under the circumstances pre- 

 vailing in dark caves, "their loss may be attributed to dis- 

 use." (Cf. "Origin pf Species," 6th ed., ch. V, pp. 128-133.) 



Morgan's comment on these elaborate speculations of Dar- 

 win is very caustic and concise. Referring to factorial muta- 

 tions, which give rise to races of flies having supernumerary 

 and vestigial organs, he says: "In contrast to the last case, 

 where a character is doubled, is the next one in which the eyes 

 are lost. This change took place at a single step. All the 

 flies of this stock, however, cannot be said to be eyeless, since 

 many of them show pieces of eye — indeed the variation is so 

 wide that the eye may even appear like a normal eye unless 

 carefully examined. Formerly we were taught that eyeless 

 animals arose in caves. This case shows that they may also 

 arise suddenly in glass milk bottles, by a change in a single 

 factor. 



"I may recall in this connection that wingless flies also arose 

 in our cultures by a single mutation. We used to be told that 

 wingless insects occurred on desert islands because those in- 

 sects that had the best developed wings were blown out to sea. 



