218 AFFINITIES AND GEOGRAPHICAL 



have taken place on land. Two principles are thus seen at 

 work in the production of the organic tenants of the earth 

 first, a gestative development pressing on through the grades 

 of organization, and bringing out particular organs necessary 

 for new fields of existence ; secondly, a variative power con- 

 nected with the will and dispositions in animals, re-acted upon 

 by external conditions, and working to minor effects, though 

 these may sometimes be hardly distinguishable from the other. 

 Everywhere along the central scale of organization, the land 

 has been, as it were, a temptation or provocation to new and 

 superior forms adapted for inhabiting it. Yv^e might almost 

 regard the progression as the result of an aspiration towards 

 new and superior fields of existence, as from the deep sea to 

 the shallow or river embouchure, from the shore to the bank, 

 from that again to the higher ground in the interior. He 

 may not yet be held as a very fanciful naturalist, who would 

 regard the megatherium as eager to climb the tree which he 

 could only shake, and thus producing a progeny fitted to do 

 that which was the object of his wishes, or the rock-nose 

 whale, which loves to rest its head oil rocks beside the beach, 

 as wishful of that mode of life which was at length vouchsafed 

 to a more highly-developed descendant. Such too may be 

 found to be the true principle of perfectibility in nature a 

 continual, though it may be an irregularly shown tendency to 

 press on to better and better powers, an indefinite improv- 

 ableness, which may work, as in seconds, in the individual, or 

 strike hours in the species. 



Within the last twenty-five years, Mr. Macleay, and other 

 naturalists, have presented a classification of animals on a 

 numerical system of grouping. The prevalent opinion amongst 

 them was, that the true divisions and subdivisions were in 

 groups of five : thus, five sub-kingdoms, five classes of verte- 

 brata, five orders of the class mammalia, and so on, the general 

 character of each class being represented in a corresponding 

 order, and the same character being further reflected even in 

 the families or genera into which the orders were subdivided. 

 There were striking appearances of a basis of truth in this 

 theory, though in the excessive ardour of its first advocates, it 

 was carried to a pitch of refinement in which nature was lost 

 sight of, and the whole was greatly marred by the notion that 

 all the groups arranged themselves in circles. Acknowledging 

 the value of the theory as, with all its faults, a great step in 

 philosophical zoology, I shall proceed to show what have an 



