616 BRITISH FOSSIL REPTILES. 



of the organs of circulation, and a progress in the extent and perfection of the lungs, 

 together resulting in the higher temperature, with more numerous and minute coloured 

 discs, of the blood. For these conditions of the vital organs characterise alike both winged 

 and wingless Birds, and the resultant unvarying warmth of the body is accompanied by a 

 clothing of down and feathers, the most exquisite and complex of all tegumentary 

 coverings, common to the Kivi and Ostrich with the Eagle and Swift. 



But there are other hypotheses of the way of operation of secondary genesis of species 

 anterior in date to that of Darwin. The influence, viz., of exercise and of disuse in altering 

 the proportions of parts mooted by Lamarck ;* the hypothesis of ' degeneration ' pro- 

 pounded by Buffon ; f and the effects of congenital changes in parts of the body, 

 mainly depended upon by the author of ' Vestiges,' in his endeavour to explain the way 

 of operation of the secondary law of the origin of species. 



The comparative ease is so refreshing, aft^r the labours of induction and dry descrip- 

 tion, in supposing a case, that I may be forgiven for indulging in a suggestion of a 

 possibility of the few still extant wingless or flightless birds having originated, not from 

 any lower cold-blooded vertebrate form, but from higher active volant members of their own 

 warm-blooded feathered class. Consideration of extinct kinds, in the restoration of which 

 I have been occupied, has strengthened the supposition. 



Here, in yielding to this indulgence, I own to finding more help from the Lamarckian 

 hypothesis than the Darwinian one, and I am ultimately led to propound the SfruthionidcB 

 as exemplifications of Buffon's belief in the origin of species by way of degeneration ; 

 on other grounds than those on M'hich my anonymous Critic, above cited (p. 614, t), views 

 the Papuan and Boschisman in relation to an antecedent higlier, indeed perfect, form 

 of man. 



Let us suppose, for example, an island affording abundant subsistence to vegetarian 

 birds, and, Jinppily for them, to be destitute of creatures able or desirous to destroy such 

 birds. If the food was wholly, or chiefly, on the surface the power of traversing such 

 surface would be of as much advantage to the bird as to the herbivorous quadruped. 

 As flight calls for more effort than course; so cursorial progression would be more 

 commonly practised in such a happy island for obtaining the daily food. The advent or 

 proximity of a known element of danger might excite the quicker mode of motion ; the 

 bird would then betake itself by a hurried flight to a safer locality. If, however, certain 

 insular birds had never known a foe, the stimulus to the use of the wings would be wanting 

 in species needing only to traverse the ground in quest of food. In the case of New Zealand, 

 for example, the roots of wide-spread ferns, being rich in farinaceous and amylaceous princi- 

 ples, the habit of scratching them out of the ground would lead to full development of the 

 muscles of the leg and foot. So, such daily habitual exercise of legs and feet by unscared 

 Rasorials would lead in successive generations to strange developments of hind-limbs ; 



* ' Philosopliie Zoologique,' 2 vols., toni. i, chaps, iii, vi, vii, 8vo, 1803. 

 j- ' Histoire Naturelle,' torn, xiv, p. 311, 4to, 1/66. 



