970 On Aquutic Carnivorous Coleoptera or Dytiscide. 
forms to which we give this collective name, but a vast number of more imperfect 
forms which there is reason to suppose may have existed in remote geological 
periods, it is quite possible—I think I. may say probable—that among such forms 
would be found the true ancestors of the present Dytiscide. But the term 
“Carabidee”” has only real scientific value imasmuch as it expresses certain 
creatures whose organization is known to us, and is expressed by a certain definition 
drawn from, and generalizing this known structure, and to apply the term Carabidze 
to include these distant and different creatures, is to alter its meaning and cannot 
but lead to logical bewilderments and mazes of a quite perplexing nature. I con- 
clude therefore, that in no correct manner can the Carabide and Dytiscidee be 
placed in a genetic relation to one another on any genealogical chart. 
On the other hand it seems quite probable that if we knew a great deal more 
than we do know about the functional values of the structures we discuss, we should 
be able to comprehend some of, if not all, the intricate affinities exhibited by the 
two families as being the result of, or correlative with, approximations in the mode 
in which function is or has been performed, and to be quite independent of genetic 
community. Thus the elongation and amalgamation of the internal laminze of the 
hind coxze along the mesial line, might be found to be connected with the fact that 
the hind legs have had to use an increased degree of force, and take a more than 
usually large share in the process of locomotion, and to act in a more directly 
horizontal direction ; this would be the case with the Dytiscidee moving through 
the water, and probably with the Pseudomorphini dwellers under the bark of trees. 
There is another question in connection with the classification of the Dytiscidee and 
Carabidze, which I may briefly allude to, although only to show the complex and 
difficult nature of the problems with which classification has to deal. It is this ; 
is it—keeping in view the intimate relation existing between these two aggregates— 
a correct course to keep them separate or should they not be in some way or other 
united? To answer this requires a valuation of structural characters of a most 
difficult nature. I will give an instance. We have in the Dytiscidze two series, 
Dytisci fragmentati and Dytisci complicati, of these the latter is distinguished by 
all its members possessing a character which is completely wanting not only to the 
other series, but to the Carabide and all the other beetles: I allude to the fact that 
four principal pieces of the body form the walls of the middle coxal cavities ; while 
the other series, Dytisci fragmentati, have these cavities formed by only three pieces. 
Now the Carabide also consist of two series distinguished by the structure of these 
cavities, the first series having, like the Dytisci fragmentati, three pieces forming the 
coxal cavity, while the second series has only two pieces entering into the com: 
position of these parts. Thus we have four series, viz., (1), Carabici second series, 
with coxal cavities formed by two pieces ; (2) and (3) Carabici first series and Dytisci 
fragmentati, with coxal cavities formed by three pieces ; and (4), Dytisci complicati 
with coxal cavities formed by four pieces. Now if we bear in mind the fact that 
