1882. ] PROF, OWEN ON THE STERNUM OF NOTORNIS. 693 
likewise included in the subclass ‘“‘ Ratite” 
logical system ? 
On a conjectural ancestral relation of the keelless 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 (Didide), 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 exert 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—‘ I] nes’y trouve aucun animal 
& 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 Diprotodon, 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, agreeably 
of a binary ornitho- 
1 Voyage et Avantures de Francois Leguat, &c. 12mo, 4 Londres, 1708, 
2 Memoirs on the Extinct Birds of New Zealand, and on those of Mauritius, 
Australia, &c. 4to, 1878. Appendix III. p. 5. 
3 Ib, Appendix I. p. 1. 
4 Trans. Zool, Soc. vol. v. 1865, p. 395, 
