Chap. II. FAMILIES. 159 



the Lepidostexis, the Polypterns, the Amia, anrl n liost of extinct genera and famihes, 

 not to speak of those families 1 liad associated with them and which Prof. Midler 

 would have removed, which, if included among Ganoids, would add still more 

 heteromorphous elements to this order. Among Decapods, we need only rememher 

 the Lobsters and Crabs to be convinced that it is not similarity of fonn which 

 holds them so closely together as a natural order. How heterogeneous Bryozoa, 

 Brachiopods, and Tunicata are among themselves, as far as their form is concerned, 

 everybody knows who has paid the least attention to these animals. 



Unless, then, form be too vague an element to characterize any kind of natural 

 groups in the animal kingdom, it must constitute a prominent feature of families. 

 I have already remarked, that orders and families are the groups upon which 

 zoologists are least agreed, and to the stud}- and characterizing of which they have 

 paid least attention. Does this not arise simply from the fact, that, on the one 

 hand, the diiference between ordinal and class characters has not been understood, 

 and onl}- assumed to be a difference of degree ; and, on the other hand, that the 

 importance of the form, as the prominent character of families, has been entirely 

 overlooked ? For, though so few natural fiimihcs of animals are well characterized, 

 or characterized at all, we cannot open a modern treatise upon any class of 

 animals Avithout finding the genera more or less naturally grouped together, under 

 the heading of a generic name Avith a termination in idee or inw indicating family 

 and sub-family distinctions; and most of these groups, however unequal in absolute 

 value, are really natural groups, though far from designating always natural families, 

 being as often orders or sub-orders, as families or sub-families. Yet thev indicate 

 the facility there is, ahnost without study, to point out the intennediate natural 

 groups between the classes and the genera. This arises, in my opinion, from the 

 fact, that family resemblance in the animal kingdom is most strikingly expressed 

 in the general fonn, and that form is an element which falls most easily under 

 our perception, even when the observation is made superficially. But, at the same 

 time, form is most difhciilt to describe accurately, and hence the imperfection of 

 most of our family characteristics, and the constant substitution for such characters 

 of features which are not essential .to the family. To prove the correctness of 

 this view, I would only appeal to the experience of every naturalist When we 

 see new animals, does not the first glance, that is, the first impression made upon 

 us by their form, give us at once a very correct idea of their nearest relation- 

 ship ? We perceive, before examining any structural character, whether a Beetle 

 is a Carabicine, a Longicorn, an Elaterid, a Curculionid, a Chrysomeline ; whether 

 a Moth is a Noctuelite, a Geometrid, a Pyralid, etc. ; whether a bird is a Dove, 

 a ^^ wallow, a Ilummiug-ljird, a Woodpecker, a Snijie, a Heron, etc., etc. But before 

 we can ascertain its genus, we have to study the structure of some characteristic 



