81 



But viewing the pelvis of the Megatherium as being the fixed centre towards which 

 the fore legs and fore part of the body w T ere drawn in the gigantic leaf-eater's efforts to 

 uprend the tree that bore its sustenance, the colossal proportions of its hind extremities 

 and tail lose all their anomaly, and appear in just harmony with the robust claviculate 

 and unguiculate fore limbs with which they combined their forces in the Herculean 

 labour. 



Finally, with reference to the hypothesis of the German authors and artists* of the 

 gradual degeneration of the ancient Megatherioids of South America into the modern 

 Sloths, it may be admitted that the general results of the labours of the anatomist in 

 the restoration of extinct species^jviewed in relation to their existing representatives!)? 

 the different continents and islands, have been such as might naturally suggest the idea 

 that the races of animals had deteriorated in point of size. Thus the palmated Megaceros 

 is contrasted, by its superior bulk, with the Fallow-deer, and the great Cave-bear with the 

 actual Brown Bear of Europe. The huge Diprotodon and Nototherium afford a similar 

 contrast with the Kangaroos and Koalas of Australia, as do the towering Dinornis and 

 Palapteryx with the small Apteryx of New Zealand. But the comparatively diminutive 

 aboriginal animals of South America, Australia, and New Zealand, which are the nearest 

 allies of the gigantic extinct species respectively characteristic of such tracts of dry land, 

 are specifically distinct, and usually by characters so well marked as to require a sub- 

 generic division, and such as no known outward influences have been observed to pro- 

 duce by progressive alteration of structure. Moreover, as in England, for example, our 

 Moles, WateT^volesv Weasels, Foxes, and Badgers, are of the same species as those that 

 coexisted with the Mammoth, Tichorhine Rhinoceros, Cave Hyaena, Bear, &c. ; so likewise 

 the remains of small Sloths and Armadillos are found associated with the Megatherium . 

 and Glyptodon in South America ; the fossil remains of ordinary Kangaroos and Wom- 

 bats occur together with those of gigantic herbivorous Marsupials in Australia; and 

 there is similar evidence that the Apteryx coexisted with the Dinornis in New Zealand. 

 I have been led, therefore, to offer the following suggestions as more applicable to, or 

 explanatory of, the phenomena than Lamaeck's progressive hypothesis of the origin of 

 species by transmutation f, or Buffon's retrograde hypothesis by degradation J. 



■• In proportion to the bulk of an animal is the difficulty of the contest which, as a 

 living being, it has to maintain against the surrounding influences which are ever tending 

 to dissolve the \ital bond and subjugate the organized matter to the ordinary chemical 

 and physical forces. Any changes, therefore, in the external circumstances in which a 

 species may have been adapted to exist, will militate against that existence in probably 

 a geometrical ratio to the bulk of such species. If a dry season be gradually prolonged, 

 the laiire Mammal will suffer from the drought sooner than the small one; if such 

 alteration of climate affect the quantity of vegetable food, the bulky Herbivore will first 

 feel the effect of the stinted nourishment ; if new enemies are introduced, the large and 



* Paadee and D'Altox, loc. cit. t Philosopbie Zoologique, 8vo 1809, torn. i. ch. vii. 



X Histoire Naturelle, 4to. torn. iv. (1766), "Degeneration des Animaux," p. 311. 



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