170 ON THE GEOGRAPHICAL DISTRIBUTION OF BIRDS. 



series," or the cotemporaneous habitants of diverse regions, Mr. Blyth regarded 

 the respective distribution of types of form as. strictly analogous ; and contended 

 that neither in the one case nor in the other was it possible to deduce universal 

 laws, though of course it was highly necessary for the naturalist to possess a 

 general knowledge of the vast accumulation of facts that had been elicited on 

 the subject, if only that he might be effectually guarded against any delusory 

 hypothesis, which a too hasty or insufficiently extensive generalization might 

 otherwise lead him to fall into. A number of instances were then t brought for- 

 ward of types peculiar to certain eras, just as, at the present time, we find that 

 others are confined to particular regions ; the location of which latter, however, 

 was shown in some instances to be of comparatively recent date, species framed 

 upon them having formerly been diffused over a more extensive area ; while in 

 other instances it would seem that the geographical limitation has remained the 

 same from a very remote period, if not from the time of their original introduc- 

 tion, of which the Kangaroos of Australia, and Lamas of South America, afforded 

 illustrative examples. Cases were also adduced of groups of species, modified 

 upon particular types of structure, to perform an especial office in the economy of 

 Nature, which office, at another period of the earth's history, appears to have 

 been fulfilled by other groups, modified upon very different types of structure ; 

 precisely as, at the present time, the Humming-birds, which are peculiar to 

 America, are represented, in the tropical and southern regions of the old Continent 

 and its islands, by analogous groups of nectar-feeding birds, of which the 

 rudimental anatomy is widely dissimilar. It was thus that the Cetacea, though 

 possessing all the essential characters of Mammalians, are modified to pass their 

 lives after the manner of fishes : on the same principle, again, that corresponding 

 groups in the different classes are observed, the part allotted to which in the 

 grand scheme of the universe is absolutely the same. 



Mr. Blyth then proceeded to explain the important difference subsisting 

 between what he designated the rudimentary and adaptive, or the intrinsical, as 

 opposed to the superficial, characters of organized, races ; the former of which he 

 affirmed to imply affinity, or physiological proximity, the latter merely what is 

 understood by the term analogy. He decidedly opposed the popular theory of 

 universal gradation (which supposes a concatenation of intermediate races, in 

 which the rudimentary characters of distinct types are blended), however 

 outward appearances might sometimes favour such a notion : the Rain-fowl 

 C Scytkrops) of New Holland, for instance, had been deemed a connecting link 

 between the Toucans and the Cuckoos; but the Toucans and Cuckoos differ 

 materially in the form of the skeleton, and in other details of their anatomy ; 

 and Scytkrops, Mr. Blyth asserted, is in every essential particular a true Cuckoo, 

 with merely a larger bill than usual, this very superficial character constituting 



