290 PROF. W. K. PARKER ON £GITHOGNATHOUS BIRDS. 
are ruled by, all these follow, those subtle early modifications of the primordial struc- 
ture of the head. 
But those who, with the new lights of morphological science, seek to help the 
classifiers, to whom they are so much indebted, do not look upon a bird as if it were a 
special creation, a new thing in the earth, standing alone, a plumy wonder. The bird 
is, as it were, but a metamorphosed hot-blooded reptile; and the reptile itself a step 
and stage upwards from a series of creatures still a little lower in the scale of life. And 
here lies the charm of the morphological study of birds, namely in the amazing meta- 
morphosis which the simple facial arches and nasal sacs undergo. It is the condition 
of these parts especially that has engaged my attention of late. ‘The postoral arches 
have, indeed, been studied by me less than those in front of and above the mouth; but 
the latter once determined and thoroughly made out, the others offer no difficulty. 
In working out the trabecular and palatine arches and nasal capsules, however, every 
refinement of histological method has to be used, and light fetched in from the mor- 
phology of the same parts in the other Vertebrata. 
In the present communication I have not been benefited alone by Professor Huxley’s 
paper just referred to, but also by another with which he favoured us on the 14th of 
May, 1868—* On the Classification and Distribution of the ‘ Alectoromorphe’ and 
‘Heteromorphe’” (see P. Z. S. 1868, p. 294). A careful study of this latter paper 
has opened my eyes to what seems to me a most vital part of these studies. I refer 
to the light they may throw upon the variation and distribution of types. This idea 
has been incubating in my own slower mind eyer since Mr. Sclater put it into my power 
to dissect the Southern type of Crow, namely Gymnorhina tibicen. 'That was eight or 
nine years since; and the Crows have always, with that light, been to me divided into 
those of the ‘‘ Notogza” and those of the “ Arctogzea.” 
Moreover the terrestrial habits and earth-born physiognomy of several of the larger 
and middle-sized Southern Passerines have attracted my attention for many years past; 
for I strongly suspected that these have had a much more direct and immediate 
struthious parentage than those highest results of metamorphic change, the songsters 
and Crows of our own hemisphere. This rooted belief has grown into something like 
certainty to me of late ; for within the present year my friend Mr. Osbert Salvin has 
put his rich collection of southern specimens of skeletons into my hands: my own 
rather extensive series consisted principally of northern types. 
These new treasures did not comprise many from Australia; but our excellent 
Senior Clerk (Mr. W. J. Williams) has given me several spirit-specimens from that 
part of the Notogea, and these have turned out to be of the utmost value. Working 
lately at the face of embryo birds to supplement morphological deficiencies in my 
paper on the Fowl's skull (Phil. Trans. 1869), I stumbled upon the remarkable 
modifications of the embryonic passerine face which give to the adult the character 
denominated by Professor Huxley, ‘“ githognathous.” This type is characterized by 
