Chap. II. SUCCESSION OF CHARACTERS. 175 



may be fully stamped upon an animal before its ordinal characters are developed. 

 Even specific characters, as far as they depend upon the proportions of parts and 

 have on that ground an influence in modifying the foi-m, may be recognized long 

 before the ordinal characters are fully developed. The Snapping-Turtle, for instance, 

 exhibits its small crosslike sternum, its long tail, its ferocious habits even before it 

 leaves the egg, before it l)reathes through lungs, before its derm is ossified to form 

 a bony shield, etc. ; nay, it snaps with its gaping jaws at any thing brought 

 near, though it be still surrounded by its amnios and allantois, and its yolk still 

 exceeds in bulk its whole body.' The calf assumes the form of the bull before 

 it bears the characteristics of the hollow-horned Ruminants ; the fawn exhibits all 

 the peculiarities of its species before those of its family are unfolded. 



With reference to generic characters, it may be said that they are scarcely 

 ever developed in any type of the animal kingdom, before the specific features 

 are for the most part fully sketched out, if not completely developed. Can there 

 be any doubt that the human embryo belongs to the genus Homo, even before it 

 has cut a tooth ? Is not a kitten, or a puppy distinguishable as a cat or a dog, 

 before the claws and teeth tell their genus? Is this not true also of the Lamb, 

 the Kid, the Colt, the Rabbits, and the Mice, of most Birds, most Reptile.s, most 

 Fishes, most Insects, Mollu.sks and Radiates? And why should this be? Simply, 

 because the proportions of parts, which constitute specific characters, are recog- 

 nizable before their ultimate structural development, which characterizes genera, is 

 completed. 



It seems to me that these facts are likely to influence the future proo-ress 

 of Zoology, in enabling us gradually to unravel more and more distinctly, the 

 features which characterize the different subordinate groups of the animal king- 

 dom. The views I have expressed above of the respective value and the promi- 

 nent characteristics of these different groups, have stood so completely the test in 

 this analysis of their successive appearance, that I consider this circumstance as 

 adding to the probability of their correctness. 



But this has another very important bearing, to which I have already alluded 

 in the beginning of these remarks. Before Embryology can furnish the means of 

 settling some of the most perplexing problems in Zoology, it is indispensable to 

 ascertain first what are typical, classic, ordinal, farail}-, generic, and specific charac- 

 ters; and as long as it could be sujiposed that these characters appear necessarily 



' I'lt. ^r. V. Neu-Wiki) quotes as a remarkable it was still a pale, almost colorless embryo, wrapped 



fact, that the Chelonara serpentina bites as soon as it up in its ftctal envelopes, with a yolk larger than 



is hatched. I have seen it snapping in the same itself hanging from its sternum, three months before 



fierce manner as it does when full-grown, at a time hatcliing. 



