90 NATUKAL SELECTION. Chap. IV. 



males, in their weapons, means of defence, or charms ; 

 and have transmitted these advantages to their male 

 offspring. Yet, I would not wish to attribute all such 

 sexual differences to this agency: for we see peculi- 

 arities arising and becoming attached to the male sex 

 in our domestic animals (as the wattle in male carriers, 

 horn-like protuberances in the cocks of certain fowls, 

 &c), which we cannot believe to be either useful to the 

 males in battle, or attractive to the females. We see 

 analogous cases under nature, for instance, the tuft of 

 hair on the breast of the turkey-cock, which can hardly 

 be either useful or ornamental to this bird; — indeed, 

 had the tuft aj)peared under domestication, it would 

 have been called a monstrosity. 



Illustrations of the action of Natural Selection. — In 

 order to make it clear how, as I believe, natural selec- 

 tion acts, I must beg permission to give one or two 

 imaginary illustrations. Let us take the case of a wolf, 

 which preys on various animals, securing some by craft, 

 some by strength, and some by fleetness; and let us 

 suppose that the fleetest prey, a deer for instance, had 

 from any change in the country increased in numbers, 

 or that other prey had decreased in numbers, during 

 that season of the year when the wolf is hardest pressed 

 for food. I can under such circumstances see no reason 

 to doubt that the swiftest and slimmest wolves would 

 have the best chance of surviving, and so be preserved 

 or selected, — provided always that they retained strength 

 to master their prey at this or at some other period of 

 the year, when they might be compelled to prey on 

 other animals. I can see no more reason to doubt this, 

 than that man can improve the fleetness of Iris grey- 

 hounds by careful and methodical selection, or by that 

 unconscious selection which results from each man trying 



