from Embryonic and Palaeozoic Data, 397 



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 tlie tribe 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 true 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 doubtless upon the impropriety of com- 

 bining 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 

 repeat, in the same class, the characteristic changes which are pecu- 

 liar to the whole family, to require any further argument to shew that 

 Palmipedes are not necessarily a natural division ; and though we 

 may fail for the present in re-arranging the families of this class into 

 natural orders, I trust after these remarks, more importance will yet 

 be attached, and more attention paid in future, to the fact that Pal- 

 mipedes, as they are now characterized, have very different types of 

 wings and bills. I have, for my own part, been strongly impressed 

 with the resemblance which exists between gulls and frigate birds, 

 and the birds of prey of the hawk and vulture families, in which 

 the toes are by no means so completely distinct as they are among 

 other birds. And, far from considering birds of prey as the highest 

 family amongst birds, I would only consider them as highest in 

 the series which includes simultaneously Procellaridae and Laridse. 

 Whether the family of pelicans belongs to this group or not, I am 

 not prepared to say ; but, at all events, the fact of their possessing 

 their four toes in one continuous web shews them to rank lowest 

 among birds. 



Again, among reptiles there will no longer be a foundation for 

 any arrangement resting merely upon impressions ; thus the ter- 

 restrial turtles will stand higher than the freshwater, and those 

 again higher than the marine ; and among Batrachians, which are 

 best known in their embryology, we can already arrange all the 

 genera in natural series, taking the metamorphosis of the higher as 

 a scale, and placing all full-grown forms in successive order, accord- 

 ing to their greater or less resemblance to these transient states. 

 Even the relative position of toads and frogs may be settled with as 

 much internal evidence as any other question of rank in wider limits, 

 merely upon the difference of their feet. 



In my researches upon fossil fishes I have, on several occasions, 

 alluded to the resemblance which we notice between the early stages 

 of growth in fishes, and the lower form of their families in the full- 

 grown state, and also to a similar resemblance between the embry- 



