VI DIFFICULTIES AND OBJECTIONS 139 



which are not rudiments of once useful organs, we cannot see 

 what there is to ensure any amount of constancy or stability. 

 One of the cases on which Mr. Romanes lays great stress in 

 his paper on "Physiological Selection" (Journ. Linn. Soc.,Yo\.xix. 

 p. 384) is that of the fleshy appendages on the corners of the 

 jaw of Normandy pigs and of some other breeds. But it is 

 expressly stated that they are not constant ; they appear 

 "frequently," or "occasionally," they are "not strictly 

 inherited, for they occiu: or fail in animals of the same litter ;" 

 and they are not always symmetrical, sometimes appearing 

 on one side of the face alone. Now whatever may be the 

 cause or explanation of these anomalous appendages they 

 cannot be classed with "specific characters," the most 

 essential featiu-es of which are, that they are symmetrical, 



of growth. But, when so reduced, the rudiment might be inconvenient or even 

 hurtful, and then natural selection would aid in its complete abortion ; in 

 other words, the abortion of the part would be useful, and would therefore be 

 subject to the law of survival of the fittest. The genera Ateles and Colobus 

 are two of the most purely arboreal types of monkeys, and it is not difficult 

 to conceive that the constant use of the elongated fingers for climbing from 

 tree to tree, and catching on to branches while making great leaps, might 

 require all the nervous energy and muscular growth to be directed to the 

 fingers, the small thumb remaining useless. The case of the Potto is more 

 diflficult, both because it is, presumably, a more ancient type, and its actual life- 

 history and habits are completely unknown. These cases are, therefore, not 

 at all to the point as proving that positive specific characters — not mere 

 rudiments characterising whole genera — are in any case useless. 



Mr. JMivart further objects to the alleged rigidity of the action of natural 

 selection, because wounded or malformed animals have been found which had 

 evidently lived a considerable time in their imperfect condition. But this 

 simply proves that th'^y were living under a temporarily favourable environ- 

 ment, and that the real struggle for existence, in their case, had not yet 

 taken jilace. We must surely admit that, when the pinch came, and when 

 perfectly formed stoats were dying for want of food, the one-footed animal, 

 referred to by Mr. Mivart, would be among the first to succumb ; and the 

 same remark will apply to his abnormally toothed hares and rheumatic 

 monkeys, which might, nevertheless, get on very well under favourable 

 conditions. The struggle for existence, under which all animals and plants 

 have been developed, is intermittent, and exceedingly irregular in its incidence 

 and severity. It is most severe and fatal to the young ; but when an animal 

 has once reached maturity, and especially when it has gained experience by 

 several years of an eventful existence, it may be able to maintain itself under 

 conditions which would be fatal to a young and inexperienced creature of the 

 same species. The examples adduced by Mr. Mivart do not, therefore, in 

 any way impugn the hardness of nature as a taskmaster, or the extreme 

 severity of the recurring struggle for existence.^ 



1 See Nature, vol. xxxix. p. 127. 



