194 LAKE SUPERIOR. 



Among birds we shall also avail ourselves of the discovery I made 

 last year, that embryos of birds have web-feet and web-wings, and no 

 longer consider Palmipedes as forming a natural group by themselves, 

 but allow the possibility of having several natural groups of birds, 

 beginning each with web-footed forms. Every one who is conversant 

 with the natural history of birds must have been struck with the great 

 diversity of features in birds united in our systems under the head 

 of Palmipedes. Taking all birds together, we hardly notice among 

 them greater differences than those which exist between the various 

 families of Palmipedes, which are, confessedly, brought together upon 

 no other character than the webbed form of their feet ; though among 

 them we have birds of prey, such as the gulls, and others, which 

 seem to stand by themselves unconnected and without any analogy 

 with any other family, such as the swans, geese, and ducks ; and 

 again, the pelicans and the genera allied to them, and also the divers. 

 It can hardly be understood why birds so widely different should be 

 brought together ; and indeed, their reunion would long ago have 

 been given up, had it not been for the difficulty of finding characters 

 to separate them, and for the strong impression, that the similarity 

 of the structure of their feet should overrule the other characters. 



But now, since it is known that birds of the most heterogeneous 

 character in the structure of their legs, in their adult form, have, 

 when very young, identical legs, whether they belong to the type 

 of hawks, or to that of crows, or to that of sparrows, or to that of swal- 

 lows, or to that of pigeons, or to that of hens, or to that of waders, 

 or to that of taue Palmipedes, when we know all these types to have 

 an identical development of their legs, and, I may add also, of their 

 wings, for the young wing is equally a small, webbed fin, there 

 can be no longer any doubt left upon the impropriety of combining 

 any two families of adult birds solely on the ground of their legs 

 having webbed feet. 



It is a fact, too well known in zoology, that different families will 



the same relation to the extremities of birds, in which also legs and wings are de- 

 veloped according to the same pattern. 



These facts have been partly described in my Lectures on Comparative Embryology, 

 and more extensively illustrated in a paper laid before the American Association for the 

 advancement of Science, in Cambridge, August, 1849. See also Narrative, p. 35. 



