37fi THE FUR SEALS OF THE PRIBILOF ISLANDS. 



first true feathers, the wintering plumage, appears, and as it covers the body the down 

 loosens and drops out. A microscopical examination of this down reveals a true 

 bunch of down rami but all united at their proximal ends in a somewhat uneven 

 manner, so that their combined mass at that point is homogeneous aiul can not be 

 separated, when fully grown, into rami parts. Figs. 10 and 11 show the structure of 

 these downs. We have thus a peculiar case (juite unlike any other North American 

 bird except the members of this order in that the first body downs are not pushed out 

 by and attached to the tips of the new feathers. 



The presence of a well-defined persistent rachis or calamus, the unciiual and 

 irregular divitling of the bases of the down rami and their nonattaclnnent, externally, 

 to the tips of the new feathers, their slow growth, and the long pei'iod of use of the first 

 true feathers, suggests that we have to do with feather coiulitions much more primi- 

 tive and degenerate than in water birds generally, and (juite difterent to those to be 

 considered later. No structure or rami bases can be seen in the rachis when full 

 grown, though as it is growing the bundles of rami fibers are distinctly to be seen 

 even to the growing end, as shown in fig. 12. Further explanation will be found with 

 the plate. 



Consideration and comparison of these feather structures and the environing 

 iiiHuences of the habitat of the species has led me to the conclusion that the cor- 

 nu)rants, with the other members of the order, occupy a nuich lower position on the 

 avian srale than the other species of this list. The very small egg, the nudity at birth, 

 the growth and character of the first ami second fe;ithering are mor[)ho]ogical charac- 

 ters, which, taken together, are so strikingly different from our other water birds as 

 to be explained only on the grouiul of the birds being less advanced, and therefore 

 HU)ie generalized. The principal use of ieatiiers is as a protection to the cuticle, 

 especially to prevent the rapid loss of body heat; therefore the great differences 

 noticeable between the feathers of land and water birds — such, for instance, as the 

 long, naiTow, Huffy, k^ss rigid and less oily feathers of the former as compared with 

 the short, broad, and more com[)act, greater curved, and more oily feathers of the 

 latter are adaptive and their use highly mechanical. It thus follows tliat differences 

 of method and sctpuMice of growth of the feathers of water birds, when the mechani- 

 cal stress due to similarity of use varies but slightly, or not at all, are of value on 

 purely morphological grounds, and suggestive of the path of their evolution. The 

 specialization of any group is due to the constant efforts of such to adai)t tliemselves 

 to minute clianges of environment during millions of years, the pathway being 

 selected by the tastes of a more or less numerous body of individuals, separate 

 bodies diverging in different directions and gradually becoming more different, tlins 

 forming other species and genera. But the slight need of fuither physiological 

 specialization of the feather growth, after having once attained a high plane, is shown 

 by the sufficiency of their development in securing an end necessary for the direct 

 preservation of the si)ecies — the prevention of the rapid loss of body heat and protec- 

 tion of the cuticle. Further changes (color and shape) must necessarily result Irom 

 the action of psychoIogic;il or psychodynamical influences. According to this view 

 the cormorant has remained at, or probably degenerated to, a lower point on the 

 avian scale than any of the other forms of this list. And this seems true also of the 

 other members of the same order, although all of them have variously differentiated 

 in the diiection of greater specialization, but not in all respects to the same extent as 



