290 PROF. W. K. PAEKEE 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 ' Alectoromorphse ' and 

 ' Heteromorphse '" (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 ever since Mr. Sclater put it into my power 

 to dissect the Southern type of Crow, namely Gymnorhina tihicen. That was eight or 

 nine years since ; and the Crows have always, with that light, been to me divided into 

 those of the "Notogeea" and those of the "Arctogsea." 



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 Notogaea, and these have turned out to be of the utmost value. Working 

 lately at the face of embryo bii-ds 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, " .Egithognathous." This type is characterized by 



