158 THE ZOOLOGIST. 
maxillo-palatine bones united (Desmognathe); in the other 
groups—and by this means he gets another perfect dichotomy, 
a positive class and a negative class—the maxillo-palatines are 
free and separate. But, unfortunately for systematists, this 
latter class contains by far the greater number of species, so that 
a further subdivision becomes necessary. The formation of the 
vomer, or ploughshare-bone of the palate, affords here definite 
characteristics; one group has the vomer pointed in front 
(Schizognathe), the other has it truncated, or cut off nearly 
square (digithognathe). 
All this while we must bear in mind that the whole classifi- 
cation is, or aims at being, simply the formation of a family- 
tree. We do not know what the primitive bird was, but we 
regard it as the trunk of the tree. After a time the birds which 
used wings diverged from those which did not; whereby we get 
two branches. One of these branches was stunted, but it bore 
strange Ostriches and Cassowaries, and such like, which do 
not concern us here. The other was imbued with a vigorous 
life. In one direction it bore Desmognathous birds—birds of 
prey, Cuckoos, Ducks, Herons, and Penguins; each grew out 
to bear twigs and sprays and leaves innumerable ; all successively 
divergent, but all tracing their descent from one particular branch. 
In another it bore birds which so soon emphasised their 
peculiarities that the great boughs bearing Schizognathous and 
Afgithognathous birds grew so strong as to form features com- 
parable to the whole of the Desmognathous ones taken together. 
Every fresh divergence sought air and space for fresh change, 
and now at the present day we must not compare adjacent leaves 
in the periphery of our family-tree, but must seek, through all 
their obvious semblance, the branch from which they severally 
spring. The leaves all point to different spots in the heavens, 
and we cannot scientifically arrange them in any linear order. 
One belongs to this family and another to that, and when we 
have to print their names in order, page after page, we must not 
expect the first of one group to bear any necessary relation to the 
last of its predecessor ; it is the group, not the individual, which 
we must compare. Regarded in this light we no longer see any 
absurdity in ranging the Smew next the Ring-Dove, for example; 
one springs from a totally different branch from the other. And 
while we must congratulate Mr. Dresser on his great endeavours, 
