416 



Royal Society : — 



first time, the student of the morphology of the skull was provided 

 with a criterion of the truth or falsity of his speculations ; and that 

 criterion was shown to be Development. 



My present object is to lay before you a brief statement of some 

 of the most important results to which the following out of the lines 

 of inquiry opened up by these eminent men seems to lead. Much 

 of what I have to say is directed towards no other end than the revival 

 and justification of their views, — a purpose the more worthy and the 

 more useful, since, with one or two honourable exceptions — I allude 

 more particularly to the recent admirable essays of Prof. Goodsir 

 — later writers on the Theory of the Skull have given a retrograde im- 

 pulse to inquiry, and have thrown obscurity and confusion upon that 

 which twenty years ago had been made plain and clear. 



I have said that the first question which offers itself is, whether 

 all vertebrate skulls are or are not, constructed upon a common plan ; 

 and in entering upon this inquiry I shall assume (what will be 

 readily granted) that, if it can be proved that the same chief parts, 

 arranged in the same way, are to be detected in the skulls of a 

 Sheep, a Bird, a Turtle, and a Carp, the problem will be solved 

 affirmatively — so far, at any rate, as the osseous cranium is concerned. 



[The author describes the general arrangement of the bony elements 

 in the cranium of the Sheep, and proceeds to compare it with that of 

 the Bird.] 



Composition of the Skull of a Bird (fig. 1). 



Fig. 1. — Longitudinal section of the Skull of a 



n this and the following sections of Crania the letters 



A.S. Alisphenoid. 

 O.S. Orhitosphenoid. 

 Pf. Prefrontal. 

 Sq. Squamosal. 

 Ep. Epiotic. 

 S.O. Supraoccipltal. 

 Pa. Parietal. 

 F. Frontal. 



B.O. Basioccipital. 

 B.S. Basisphenoid. 

 P.S. Presphenoid. 

 Eth. Ethmoid (lamina per 



pendicularis). 

 E.O. Exoccipital. 

 M. Mastoid. 

 P. or P.S. Petrosal. 

 1\M. Petroniastoid. 



young Ostrich. 



have the same meaning. 



Foramina for nerves. 

 1 . Olfactory ; 2. optic ; 3 

 &4. oculomotor and pa- 

 thetic nerves ; 5. third 

 division of trigeminal ; 

 7. portio dura and mol- 

 lis ; 8. pneumogastric ; 

 Epiph. Pineal gland, or 

 epiphysis cerebri. 



