the young were 'altricial' or 'præcocial,' nidicolous or nidifugous, thus creating an entirely arbitrary system of the same value as those other systems based upon the form of the bill, shape of the wing and so on. The post-Darwinians, working on the lines of evolution, see in these very different conditions, a phylogenetic significance, and regard the nidifugous as more reptilian than the nidicolous young. Consequently, those groups which have nidifugous young are to be regarded as standing comparatively low in the scale, whilst those with nidicolous young must be considered to have risen to a higher plane. This newer view is undoubtedly an improvement on the older, but il must, we think, give place to a yet wider interpretation.
If we turn from the purely systematic point of view to the more philosophical side of the question, as it at present stands, we shall, I think, find an equally unsatisfactory state of affairs. The two most recent text-books of zoology may be cited as authorities.
According to Jordan and Kellogg ('Animal Life,' 1901), 'those animals are highest in development, with best means of holding their own in the struggle for life, that take best care of their young,' and 'among the lower or more coarsely organized birds, such as the chicken, the duck, and the auk, as with reptiles, the young animal is hatched with well-developed muscular system and sense organs, and is capable of feeding itself,' but the offspring of the 'more highly organized forms, such as the thrushes, doves, and song-birds generally' are hatched in a wholly helpless condition, with ineffective muscles, deficient senses, and dependent wholly upon the parent. Similarly Shipley and MacBride write: "The manner the young are cared for is a most important feature. . . . The just-hatched young of the Pheasant and Game-birds are able to run about and look after themselves, whereas those of the Passeres or Songsters, require constant care and attention for a long time. These last are considered. . . to be the most highly developed of all birds, both as to their intellects and their flying powers, so that it is hardly too much to say that the increasing sacrifice of the parents on behalf of the young has had its reward, in the improvement it has brought about in all the faculties of the race."
Those who are responsible for the views just enunciated appear to have forgotten that the cormorants, for example, also bring their young into the world blind, naked and helpless, and not infrequently rear them in a nest of sticks on tree tops; yet the warmest admirer of these birds can not claim for them either a high degree of organization or great intelligence among birds. Their near allies, the darters, gannets, tropic and frigate birds also have helpless young, which in the case of the frigate birds and darters are also reared in nests in trees. We might multiply instances, but these are sufficient for our
