CHAPTER VI 
DIFFICULTIES AND OBJECTIONS 
Difficulty as to smallness of variations—As to the right variations occur¬ 
ring when required—The beginnings of important organs—The mam¬ 
mary glands—The eyes of flatfish—Origin of the eye—Useless or 
lion-adaptive characters—Recent extension of the region of utility in 
plants—The same in animals—Uses of tails—Of the horns of deer— 
Of the scale-ornamentation of reptiles—Instability of non-adaptive 
characters—Delbceuf’s law—No “specific” character proved to be 
useless—The swamping effects of intercrossing—Isolation as prevent¬ 
ing intercrossing— Gulick on the effects of isolation—Cases in which 
isolation is ineffective. 
In the present chapter I propose to discuss the more obvious 
and often repeated objections to Darwin’s theory, and to show 
how far they affect its character as a true and sufficient 
explanation of the origin of species. The more recondite 
difficulties, affecting such fundamental questions as the causes 
and laws of variability, will be left for a future chapter, after 
Ave have become better acquainted with the applications of the 
theory to the more important adaptations and correlations of 
animal and plant life. 
One of the earliest and most often repeated objections was, 
that it was difficult “ to imagine a reason why variations tend¬ 
ing in an infinitesimal degree in any special direction should 
be preserved,” or to believe that the complex adaptation of 
living organisms could have been produced “ by infinitesimal 
beginnings.” Now this term “infinitesimal,” used by a well- 
known early critic of the Origin of Specie -, was never made use 
of by Darwin himself, who spoke only of variations being 
“slight,” and of the “small amount” of the variations that might 
be selected. Even in using these terms he undoubtedly afforded 
