4 REPORT — 1881. 



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single species. The dog and jackal, for instance, are now regarded as 



two sjjecies, bat if a sei'ies of links were discovered between tliem they 

 would be united into one. Hence in tbia sense there never can be links 

 between any two species, because as soon as the links are discovered the 

 species are united. Every variable species consists, in fact, of a number 

 of closely connected links. 



But if the geological record be imperfect, it is still very instructive. 

 The further paleeontology has progressed, the more it has tended to fill 

 up the gaps between existing groups and species : Avhile the careful 

 study of living forms has brought into prominence the variations 

 dependent on food, climate, habitat, and other conditions, and shown 

 that manj- species long supposed to be absolutely distinct are so closely 

 linked together by intermediate forms that it is difBcult to di'aw a 

 satisfactory line between them. Thus the European and American bisons 

 are connected by the Bison priscus of Prehistoric Europe ; the grizzly 

 bear and the brown bear, as Busk has shown, are apparently the 

 modern representatives of the cave bear ; Flower has pointed out the 

 pala;outological evidence of gradual modification of animal forms in the 

 Artiodactyles ; and we may almost say, as a general rule, that the earliest 

 known mammalia belong to less specialised types than our existing species. 

 They are not well-marked Carnivores, Rodents, Marsupials, &c., but rather 

 constitute a gi'oup of generalised forms from which our j^i'esent well- 

 marked orders appear to have diverged. Among the Invertebrata, Car- 

 penter and Williamson have proved that it is almost impossible to divide 

 the Foraminifera into well-marked species; and, lastly, among plants, 

 there are large genera, as, for instance, Rubus and Hicracium, with 

 reference to the species of which no two botanists are agreed. 



The principles of classification point also in the same direction, 

 and are based more and more on the theory of descent. Biologists en- 

 deavour to arrange animals on what is called the ' natural system.' No 

 one now places whales among fish, bats among birds, or shrews with mice, 

 notwithstanding their external similarity ; and Darwin maintained that 

 ' community of descent was the hidden bond which naturalists had been 

 unconsciously seeking.' How else, indeed, can we explain the fact that 

 the framework of bones is so similar in the arm of a man, the wing 

 of a bat, the fore-leg of a horse, and the fin of a porpoise — that the 

 neck of a giraffe and that of an elephant contain the same number of ver- 

 tebrse ? 



Strong evidence is, moreover, afforded by embryology ; by the presence 

 of rudimentary organs and transient characters, as, for instance, the 

 existence in the calf of certain teeth which never cut the gums, the 

 shrivelled and useless wings of some beetles, the presence of a series of 

 arteries in the embryos of the higher Vertebrata exactly similar to thos6 

 which supply the gills in fishes, even the spots on the young blackbird, 

 the stripes on the lion's cub ; these, and innumerable other facts of the 

 same character, appear to be incompatible witl\ tUe idea that each species. 



