NATURAL SCIENCES OF PHILADELPHIA. 195 



certain doubtful cases will probably be decided by reference to it. It draws a 

 sharp, if here and there a broken, line between Gallinie and Columbx. It sepa- 

 rates, with precision. Herons and their allies from other Grallce. It goes some 

 way in distinguishing lamellirostral from other Natatores ; and other instances 

 of its application might be cited. 



Some other points are to be considered in this connection. The various 

 conditions of single, double, and middle monogamy, and polygamy, are to be 

 regarded. Some generalizations, apparently important, may be drawn from 

 the comparative size of the air-space in the eggs of the two series.* AUriccs 

 usually lay few eggs, Prascoces many; an evident ^adaptation to facilities of 

 caring for young under the two regimes. Yet an immense group of prascoces 

 — Grallx — lay but four, which is below the average of altricial Insessores. 

 There are also many families among Rasores and higher Grollse, — too many to 

 be considered as exceptions proving a rule, — in which altricial or prtecocial 

 characters are but doubtfully e.xpressed, or else do not agree with unquestion- 

 able affinities in other respects. Finally, it should be observed that, as all 

 Insessores are altrices, no parallelism exists between the great majority of ex- 

 isting birds and the priEcocial series of walkers, waders and swimmers, the 

 relationships between which and Insessores, if any, are only of remote analogy, 

 not affinity. To speak figuratively : we come a long way, — the greater part 

 of the whole way — down the bird scale, before meeting with any indications 

 of difference in this physiological point. Arrived at the lower walkers, and 

 higher waders, we first dimly see a certain principle striving, with uncertain 

 results, to assert itself. Wavering for a while, at length it gains force and 

 effects fissuration of birds into two or more "parallel" — i. e., self-repeating or 

 self-representing — series; the main stem continues unaltered, through wading 

 Herons to swimming Tolipalmi, Longipenncs, kc. ; the fork, first distinct among 

 some walkers, thence continuing through the smaller Grallie, &c., to anatiform 

 swimmers. This is a matter of observation, not an hypothesis; is it sufficient 

 basis for a primarj^ division of birds ? 



In the application of Bonaparte's principle to our subject of swimming birds, 

 the results are seen to be no better than was to have been expected. It is diffi- 

 cult to say which one of this author's many schedules, variously modified, 

 should be held most expressive of his views. That given in the Comptes 

 Rendus of Oct.31, 1853, probablydoes his^classification the most justice. Here 

 water birds form his sixth order, Gavix, comprehending Tolipalmi and Longi- 

 pennes, and his tenth, Anseres, including all other Natatores. The two groups 

 are separated by all the Rasores, the Struthious birds, and all the Grallse ex- 

 cept Herons. Beyond question, swimming birds, however viewed as to their 

 subdivisions, cannot be separated thus ; the steganopodous and macropterous 

 Natatores cannot be separated from others by three, or by any, orders. Here 

 they are made to differ more from other swimmers than the Gallinaceous and 

 Grallatorial birds do. The structural differences between a penguin and a 

 duck are certainly as great as those between an auk and a cormorant ; yet in 

 one instance the birds stand side by side in the system, in the other they are 

 divided by intervention of three diverse orders. But a more serious objection 

 to this schedule, and one, too, coming from the author's own side of the ques- 

 tion, is found in the fact that Urinatores are not all Prsecoces, as they were 

 in this place represented. They were consequently subsequently referred to 

 Gavice, and the penguins made a distinct order. But it so happens, unfortu- 

 nately or otherwise, that neither are the Urinatores, with or without tlie pen- 

 guins, all Altrices. In short, birds will not lie conformably disposed in the 

 two Procrustean beds of Altrices and Friecoces. As far as known, all Insessores 

 (qu. Columbie ?), Herodiones, Steganopodes, and Longipennes are Altrices ; St?-ti- 

 thiones and Lamellirostres are Prrecoces ; beyond these, neither can be safely 

 predicated of groups of higher rank than families, without exceptions and re- 

 servations. 



1869.] 



* Cf., e. g., G. A. Lewis' Lectures on Ornithology, pt. i, p. 17. 



