1882.] PROF. OWEN ON THE STERNUM OF NOTORN1S. 693 



likewise included in the subclass " Ratita "' of a binary ornitho- 

 logical system ? 



On a conjectural ancestral relation of the kcelless external cha- 

 racter to the present advanced volant faculty of the Avian class, the 

 Dodo had made some progress thereto from its assumed " ratite " 

 progenitor : it had risen to the rudiment of a keel. 



To this conclusion, however, another conjecture opposes itself. 

 Dodos (Dididce), having gained in bulk and weight upon other 

 geographically associated birds of their own family or genus, and 

 finding sufficient sustenance on the ground, with convenience for 

 nidification, had no call to e.xert the strenuous act of flight. The 

 stimulus thereto, which we daily witness in birds about us, was 

 wanting. There were no enemies, quadrupedal or bipedal, in the 

 tract of land now reduced to the islands of Mauritius and Rodriguez, 

 to disturb their wellbeing and threaten their existence. 



I have elsewhere remarked, as bearing upon the interesting ques- 

 tion of the relation of the simplified sternum to the genesis of Birds, 

 that Pezophaps, the largest land-bird seen by the early settlers in 

 the island of Rodriguez, " differed in no other respect from the 

 class-rule in other birds, save in the inability to fly by the action of 

 the fore limbs. There were no enemies, native to the island, able to 

 take advantage of that disablement — ' II ne s'y trouve aucun animal 

 a quatre pieds, que des rats, des lezards, et des tortues de terre,' writes 

 Leguat in his interesting little book'. The ' Solitaires ' had no call 

 to practise or to endeavour to practise that hardest mode of locomo- 

 tion to obtain sustenance or fulfil any of the conditions of preserva- 

 tion of the individual or of the species ; they were never scared into 

 the violent volant exercise"". The exiled Huguenots derived the best, 

 if not largest, proportion of their animal food from the wingless birds 

 of Rodriguez. 



The advent of Man, with or without a subservient carnivorous 

 quadruped, is an intelligible cause of the extinction of species, espe- 

 cially of birds attracting his hunger by their size and unable to escape 

 by flight. Thus the huge wingless Dromornis^, like Biprotodon, has 

 become known to us only by the osseous remains in Australia. The 

 smaller Emu and Cassowary are there restricted in range and num- 

 bers, and seem to be gradually passing away. 



The fact of a range of variety in size has been determined in the 

 individuals of many species. Such variety affecting a Cereopsis 

 Goose to the degree shown by Cnemiornis* would, in a corresponding 

 degree, render the act of flight more difficult and laborious. Con- 

 sequently, if that act were not needed for the acquisition of food, it 

 might seldom or never be exercised in the absence of any enemy from 

 which it would offer a way of escape. By long disuse of the "wings, 

 continued through successive generations, those organs, agreeablv 



' Voyage et Avantures de Fran(,ois Leguat, &c. 12mo, a Londres, 1708. 

 ^ Memoirs on the Extinct Birds of New Zealand, and on tliose of Mauritius, 

 Australia, &c. 4to, 1878. Appendix III. p. .'i. 

 ^ lb. Appendix I. p. 1. 

 •■ Trans. Zool. Soe. vol. v. 186.5, p. m?>. 



