THE VEGETABLE AND ANIMAL KINGDOMS. 157 



from that which is commonly presented, when we see a 

 single peculiar individual standing in the midst of, and neces- 

 sarily allying itself to, the original stock. The process of 

 variation as a consequence of changed conditions and appe- 

 tencies being left unchecked, and that for a vast space of time, 

 we obtain at length creatures fixedly peculiar ; that is, however, 

 creatures which merely appear so, because there is no replacing 

 them in the former conditions in this densely-peopled globe, 

 and, though there were, the retrogression to the anterior forms 

 would require a space of time beyond the range of human 

 observation. 



It may now be remarked, that, in this hypothetic variability, 

 the possibility of re-union may, and in all probability does, 

 depend upon the degree of similarity which still exists in the 

 different individuals, supposing them to be members of the 

 same stirps or line of being, for I believe that no others are 

 capable of intermixture. As has been remarked by a venerable 

 naturalist " Many bulbous roots that have been increased 

 during a long succession of years by offsets, become absolutely 

 incapable of bearing seed ; and it is not more strange that 

 plants which in different soils and climates have diverged from 

 the original form of the first created individual, should refuse 

 to bear seed by the one which has departed most widely, and 

 yet produce it readily by another, which still agrees with it in 

 some important points." 1 Admit this, and the grand basis of 

 specific distinction, the possibility of intermixture, can no 

 longer be laid hold of. Plants and animals of one line are 

 only to be expected to unite, which being of one grade of 

 organization, are also sufficiently near to each other in those 

 peculiarities liable to modification from external causes, on 

 which the so-called distinctions of species are grounded. 2 



The illustrations of our hypothesis are now closed. We 

 have seen that, even judging from short spaces of time, there is 

 a great and incontestable modifiability of organic forms, so 

 great as to have absorbed the presumed distinctions of species 

 in many noted instances. It appears that this modifiability, 

 by some hidden law, immediately obeys external conditions. 

 It has also been seen that, though no transition from grade to 

 grade was ever observed to take place, the means and mode by 

 which it might naturally happen are not concealed from us ; 



1 Letter of the Dean of Manchester in Gardeners' Chronicle, July 18, 

 1846. 



2 See Proofs and Illustrations, No. 11. 



