ORIGIN OF SPECIES 93 



colour from white to seaweed brown, or by projecting into 

 the water a cloud of ink? Our forefathers, watching this 

 inevitable tyranny of strength and cunning, felt that it was 

 cruel. As it had been in the past it must continue to be. 

 The weak would remain weak ; the strong would continue 

 strong. We lose the idea of cruelty in the interest of the 

 competition. It is a race for perfection, and the things 

 which fail to adapt themselves must become as the grap- 

 tolites, trilobites and ammonites, which have long since 

 disappeared from the earth. 



Further, what is true of living things, looked at as a 

 whole, is true of every organ of which they are composed. 

 Fifty years ago it was the custom for the teacher of human 

 anatomy, after saying all that could be said about the form 

 and structure of the organs which were the subjects of the 

 lesson for the day, to dwell upon their perfection as instru- 

 ments designed for a particular work. He may have had 

 his doubts, but it would have been irreverent to express 

 them. Now, when he touches upon the mechanics of a 

 bone, say the scapula, or of a muscle such as the plantaris, 

 he is free to say of the former, ' ' This bone is entirely wrong 

 in principle, but as an adaptation of the scapula of a quad- 

 ruped, which is used to transfer the weight of the trunk to 

 the fore limb, it serves its purpose, namely, to swing the 

 fore limb on the trunk." Or of the latter, "This is a 

 muscle which was of use in lower animals. It is practically 

 useless in Man, and will, in course of time, be discarded. Its 

 poor development and irregular origin and insertion show 

 that it is on the point of disappearing." There is not an 

 organ in the body which is perfect, in the sense of having 

 attained to finality, and there are many which are evidently 

 on the downward grade. Take, as an example, the thymus 

 gland, an organ which lies behind the upper part of the 

 breastbone. At the time of birth this organ weighs about 

 half an ounce. During the first two years of life it grows as 

 fast as other organs ; after five it rapidly disappears. It 



