212 Mr. A. R. Wallace on the Natural Arrangement of Birds. 



on the one side, and the Woodpeckers and Parrots on the other, 

 but rather nearer to the former than the latter. If, on the other 

 hand, we place this group among the Conirostres, we can give 

 no such satisfactory account of its structural affinities. Swainson 

 places it between the FringillidcB and the Bucerida. The former 

 have all well-formed Passerine feet, the hind toe always well 

 developed, and the outer toe never so long as the middle one ; 

 they have generally powerful wings, and are of such a uniformly 

 small size as not even to give them an appearance of affinity 

 with the Turacos and Musophagida. The Hornbills are if pos- 

 sible still further removed, as our previous account of their 

 habits and the structure of their feet will at once show. We 

 cannot believe that so very acute and observant a naturalist as 

 Mr. Swainson could have been led to propound these as natural 

 affinities, had he not been blinded by his belief in the universal 

 existence in nature of a numerical and circular arrangement, 

 which, without disproving it in any particular cases, we believe 

 can be shown to be absolutely untenable on two general grounds. 

 1st. Geological investigations prove that the animals now exist- 

 ing on the earth are probably not one-tenth, perhaps not one- 

 hundredth, of those which have existed; for all before the Tertiary 

 epoch were of different species and mostly of different genera, 

 and thousands of other genera, families, and whole orders must 

 have existed of which we are absolutely in ignorance. If there- 

 fore this regular system were true of the whole, it must be quite 

 imperceptible in the mere fragment we have an acquaintance 

 with. Instead of complete circles being the rule, they should 

 scarcely ever exist ; in fact, the gaps left in the system by its 

 authors do not leave room enough for all the forms that must 

 have become extinct. 2ndly. This system absolutely places limits 

 to the variety and extent of creation ; for it is said that every 

 group can only contain five subgroups, and the number of gra- 

 dations of groups is fixed. For instance, in a family there can 

 be only five subfamilies, in each of which there can be only five 

 true genera, and again in each genus five subgenera. In the 

 Psittacida therefore there can be but twenty-five generic forms, 

 and when those are all known, not only is it declared to be im- 

 possible to discover a new one, but it is also asserted that no 

 others can possibly ever have existed and become extinct. This 

 is the logical deduction from any system of definite numbers in 

 natural history, and it is one that should convince every person 

 of the false basis on which all such systems rest. 



Having determined the position of the Turacos, we shall next 

 have to consider that remarkable bird, the Opisfhocomus cristatus. 

 This has been and still is placed among the Gallinacese by most 

 continental authors. Mr. G. R. Gray, however, places it near the 



