232 NATURAL HISTORY. 



various means of their concealing or defending their 

 honey from insects, and their seeds from birds. On 

 the other hand, swiftness of wing has been acquired 

 by hawks and swallows to pursue their prey; and a 

 proboscis of admirable structure has been acquired by 

 the bee, the moth, and the humming-bird, for the 

 purpose of plundering the nectaries of flowers. All 

 which seem to have been formed by the original living 

 filament, excited into action by the necessities of the 

 creatures which possess them, and on which their 

 existence depends.' 



It is a matter of great interest to note in the fore- 

 going passage that Erasmus Darwin had got hold of 

 one side of the principle which his grandson subsequently 

 elaborated into his theory of * Sexual Selection' the 

 principle, namely, that certain structural peculiarities can 

 be acquired, and when acquired may be intensified in 

 the process of inheritance, owing to the fact that only 

 those males possessing the peculiarity have the oppor- 

 tunity of leaving descendants. Erasmus Darwin, how- 

 ever, ascribed to a 'final cause' what Charles Darwin 

 would have regarded as a result. We also see in the 

 above, that Erasmus Darwin clearly recognised the 

 significance and importance of what are now called 

 'protective resemblances.'* On the other hand, he 

 curiously inverts the case where he speaks of the con- 

 trivances by which plants protect or conceal their honey 

 from insects; and no one has done more than his own 



* In other passages he gives a much fuller account of protective resemblances 

 among animals, and adduces many instances, as to which he says that though the 

 'final cause' is easily understood, 'the efficient cause would seem almost beyond 

 conjecture.' 



