228 NATURAL HISTORY. 



mitted to their offspring, but that even some of the 

 habits of the parents may be similarly handed on to the 

 young. It is only, he remarks, from the imperfection 

 of language that we speak of a young organism as being 

 a new animal. The young animal is ' in truth a branch 

 or elongation of the parent ; since a part of the embryon- 

 animal is, or was, a part of the parent; and therefore 

 in strict language it cannot be said to be entirely new at 

 the time of its production.' 



In the third place, he divined that the community of 

 fundamental structure which can be shown to underlie 

 the differences which separate different groups of animals, 

 affords an d priori presumption in favour of a community 

 of descent for these groups. On this point, he remarks : 

 'When we revolve in our minds the great similarity of 

 structure which obtains in all the warm-blooded animals, 

 as well quadrupeds, birds, and amphibious animals, as 

 in mankind; from the mouse and bat to the elephant 

 and whale; one is led to conclude that they have been 

 alike produced from a similar living filament.' 



Up to this point, then, Erasmus Darwin had obviously 

 grasped several of the leading principles in the modern 

 theory of the Origin of Species by ' descent with modifica- 

 tion.' He understood the principles of variation and 

 inheritance, and he comprehended the importance of 

 'homologous' structures as proving blood-relationship. 

 Some of his further views, however, were more akin to 

 those afterwards put forth by Lamarck than to those 

 which were expounded by his illustrious grandson in 

 the ' Origin of Species by means of Natural Selection.' 

 Thus, he seems to have thought that interbreeding 



