J. E. DUBRDEN 179 



It may be held that some mechanical advantage to the bird has 

 accrued from the loss of the three toes in the matter of rapid movement, 

 and that this will be increased still further when the small fourth dis- 

 appears: for then the bird will have the same single-toed foot as the 

 horse, which many writers deem to be a forcible example of a purposeful 

 adaptive change. But if the interpretation here given of the loss of 

 scales from the third toe be correct, namely, that it is the first hint 

 of a degeneration which the toe is about to undergo, then retrogression 

 will not cease with the disappearance of the fourth, and the temporary 

 advantage from the possession of only the middle toe will ultimately be 

 changed to one of real disaster by the continued action of the same 

 degenerative force ; certainly a vital argument against the notion of any 

 purposeful significance in the retrogressive changes. 



On the whole we are forced to conclude that no necessary connection 

 exists between the degenerative losses in the ostrich and the welfare of 

 the bird ; they are changes which have taken place apart from any 

 adaptive considerations, and in the main are indifferent as regards 

 the every-day life of the bird. Incidentally they may come to have 

 an adaptive significance, but it is just as likely to be harmful as 

 beneficial. 



During the course of its existence, even from the egg stage onwards, 

 the ostrich is so surrounded with dangers that, compared with them, any 

 slight structural variation must have an infinitesimal selection value. 

 The position of the nest, often containing scores of eggs, is never 

 determined by any concealing or protective consideration ; jackals and 

 hyaenas show a wonderful aptitude in rolling the eggs about until they 

 break, or of being on hand as the chicks hatch, hardly deterred by the 

 frantic display of the parents to drive them away. Some slight parental 

 care is manifested for the chicks as a whole, but an utter indifference to 

 the fate of the individual. A spell of cold, wet weather in the absence 

 of an oiled compact plumage is likely to be fatal ; parasites, such as 

 tape-worm and strongyles, abound and play havoc during any reduced 

 state of nutrition, as from a period of drought ; aspergilliosis has pre- 

 vented many a farmer from rearing a single chick season after season ; 

 and in nature camivora, large and small, are always at hand to exact 

 their toll. With all these chances against the attainment and con- 

 tinuance of adult life it seems absurd to maintain that a slight reduction 

 in the number of plumes, a lessening of the number of scales or the claw 

 on the toes, or a slight diminution in the size of a phalanx could count 

 as having survival values. Further, on the wide expansive plains of 



