44 EVOLUTION 



of the same old materials, and it is Nature's 

 conjuring there is something new every 

 time. But the facts being so, it is very 

 difficult to suggest any interpretation except 

 one that the resemblance is due to blood- 

 relationship. As Darwin said: 'How inex- 

 plicable is the similar pattern of the hand of 

 a man, the foot of a dog, the wing of a bat, 

 the flipper of a seal, on the doctrine of in- 

 dependent acts of creation! How simply 

 explained on the principle of the natural 

 selection of successive slight variations 

 in the diverging descendants from a single 

 progenitor ! ' 



NEW ORGANS FROM OLD. Another set of 

 suggestive facts is found in what the compara- 

 tive anatomists have shown in regard to 

 many of the structural novelties which ap- 

 pear at point after point in the animal series, 

 that they are old organs in a new guise. The 

 poison gland of a snake is usually a specializa- 

 tion of the parotid salivary gland; the milk- 

 glands of ordinary mammals are specializa- 

 tions of the sebaceous glands of the skin, while 

 those of the egg-laying duckmole and spiny 

 ant-eater are nearer the sweat-gland type; 

 the chain of three minute bones in the mam- 

 malian ear, conveying vibrations from the 

 drum to the inner ear, is in a sense quite new, 

 and yet its links were forged long before there 





