LEADING GROUPS OF EXISTING SYSTEMS 185 



order; for instance, young Hemiptera, young Orthoptera may safely 

 be referred to their respective families from the characteristics they 

 exhibit before they show those peculiarities which characterize them 

 as Hemiptera or as Orthoptera; young Fishes may be known as mem- 

 bers of their respective families before the characters of their orders 

 are apparent, etc. 



It is very obvious why this should be so. With the progress of the 

 development of the structure the general form is gradually sketched 

 out, and it has already reached many of its most distinctive features 

 before all the complications of the structure which characterize the 

 orders have become apparent; and as form characterizes essentially 

 the families, we see here the reason why the family type 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 gTound an influence in modifying the form, 

 may be recognized long before the ordinal characters are fully devel- 

 oped. The Snapping-Turtle, for instance, exhibits its small crosslike 

 sternum, its long tail, its ferocious habits even before it leaves the 

 egg, before it breathes through lungs, before its derm is ossified to 

 form a bony shield, etc.; nay, it snaps with its gaping jaws at anything 

 brought near, though it be still surrounded by its amnios and allan- 

 tois, and its yolk still exceeds in bulk its whole body.^^ The calf as- 

 sumes 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 [if] ever developed in any type of the animal kingdom be- 

 fore 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 

 Reptiles, most Fishes, most Insects, Mollusks and Radiates? And why 



^ Prince Maximilian von Wied-Neuwied quotes as a remarkable fact that the 

 Chelonara sperpentina bites as soon as it is hatched. I have seen it snapping in the 

 same fierce manner as it does when full grown, at a time when it is still a pale, almost 

 colorless embryo, wrapped up in fetal envelopes, with a yolk larger than itself hanging 

 from its sternum, three months before it is hatched. 



