188 Mr. H. E. Strickland on the Natural By stem 



cations of structure which constitute the characters of groups 

 were given solely with reference to the external circumstances 

 in which the creature is destined to live, it follows that the 

 irregularities of the external world must be impressed upon 

 the groups of animals and of plants which inhabit it. The 

 supply of organic beings is exactly proportioned to the de- 

 mand ; and Nature does not, for the sake of producing a re- 

 gular classification, go out of her way to create beings where 

 they are not wanted, or where they could not subsist. Thus, 

 for instance, the warm climate and varied soil of the tropics 

 admits of the growth of a vast variety of flowers and fruits. 

 The group of Humming-birds which feed on the former, and 

 of Parrots which feed on the latter, are accordingly found to 

 be developed in a vast variety of generic and specific forms ; 

 while the family of Gulls which seek their food in the mono- 

 tonous and thinly inhabited regions of the north, are few in 

 species and still fewer in genera. Again, the variety of plants 

 in the tropics admits the existence of a great variety of in- 

 sects, and the family of Woodpeckers is proportionately nu- 

 merous; while the Oxpecker (Buphaya), which seems to form 

 a group fully equivalent in value to the Woodpeckers, is 

 limited to but one or two species, because its food is confined 

 to a few species of insects which only infest the backs of 

 oxen. 



It follows, then, that the groups of organized beings will be 

 great or small, and the series of affinities will be broken or 

 continuous, solely as the variations of external circumstances 

 admit of their existence, and not according to any rule of 

 classification. If, indeed, we were to imagine a world laid 

 out with the regularity of a Chinese garden, in which a cer- 

 tain number of islands agreeing in size, shape, soil, and form 

 of surface, were placed at exactly equal distances on both 

 sides of the equator, we might then conceive the possibility 

 of a perfect symmetry in the groups of beings which inhabit 

 them ; but without some such supposition, I do not see how 

 a class of animals or plants can be symmetrical in themselves, 

 and yet be expressly adapted for conditions of existence which 

 are eminently irregular. 



3. To pass from syllogism to induction, it is most certainly 

 not the case that any definite number or geometrical property 

 runs through the animal or vegetable kingdom. I do not 

 wish on the present occasion to enter on any criticism of in- 

 dividual systems, but it would be easy to show that no sym- 

 metrical system yet proposed is a true picture of the real 

 series of affinities. Without referring to the numerous gaps 

 in these systems which are referred by their authors to species 



