414 Royal Society : — 



insufficient for specialties, as, if they were acknowledged, the entire 

 units of this protean variety must be promoted to the rank of species. 

 I do not contend that good species may not be found in company ; 

 for the Chem. Sandvicensis, Ch. plicata, and others are often seen 

 with it ; but their characters are so decided as to admit of no doubt 

 of their distinctness. 



Mr. Jeffreys, in the "Gleanings," says that I have found a speci- 

 men of Mr. Alder's O. nitida : I thought so too ; but on examina- 

 tion after his departure, it turned out to be one of my protean dwarf 

 ''pallidar 



I cannot admit that the O. turrita (Jeffreys) has been taken by 

 me at Exmouth ; the shells he has mistaken for his object are varie- 

 ties of Chem. acuta, the animal of which I have often examined. 



Mr. Jeffreys, speaking of his O. minima in the January " Annals" 

 for 1858, PI. 2. f..3, says its nearest ally is perhaps O. cylindrica : 

 he is quite right. I showed him, under the microscope, at my house, 

 that it was an undoubted slender O. cylindrica ; but he seemed in- 

 disposed to concur with me. 



In the notice of the above articles, I trust I have not out- 

 stepped the bounds of a fair and legitimate commentary. 

 I am, Gentlemen, 



Your most obedient Servant, 



Wm. Clark. 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL SOCIETY. 



November 18, 1858. — Richard Owen, Esq., V.P., in the Chair. 



*'0n the Theory of the Vertebrate Skull," being an Abstract of 

 the Croonian Lecture. By Thomas H. Huxley, Esq., F.R.S. 



(Abstract.) 



I apprehend that it has been, and is, too often forgotten that 

 the phrase " Theory of the Skull " is ordinarily employed to denote 

 the answers to two very different questions : — the first. Are all verte- 

 brate skulls constructed upon one and the same plan 1 the second, 

 Is such plan, supposing it to exist, identical with that of the verte- 

 bral column ? 



It is also forgotten that, to a certain extent, these are inde- 

 pendent questions ; for, though an affirmative answer to the latter 

 implies the like reply to the former, the converse proposition by no 

 means holds good, an affirmative response to the first question being 

 perfectly consistent with a negative to the second*. 



* There is a wide difference, too, in the relative importance of either question 

 to the student of comparative anatomy. Unless it can be shown that a general 

 identity of construction pervades the multiform varieties of vertebrate skulls, a 

 concise, uniform, and consistent nomenclature becomes an impossibility, and the 

 anatomist loses at one blow the most important of aids to memory, and the most 

 influential of stimulants to research. The second question, on the other hand, 

 though highly interesting, might be settled either one way or the other without 

 exerting any very important influence on the practice of comparative anatomy. 



