ANDREWS — ON THE GREENLAND BTTLLHEAD. 2 23 



important scale than anatomists hare as yet suspected. The change 

 amounts to the addition of a double convex lens of crown glass, having 

 a radius of a third of an inch ; while the elongation principle would re- 

 quire the lengthening of the chamber from one inch to two inches and 

 three-quarters. Anatomists have not as yet discovered a mechanism for 

 changing the shape of the lens sufficient to produce those results. The 

 lens should be almost turned into a sphere ; and he knew of no ciliary 

 muscles capable of effecting so great a change. 



Captain Hutton suggested that the pressure of muscles upon the lenses 

 of the eye might, perhaps, alter the density and refractive powers of the 

 humours inside the lenses. 



Mr. Lalor observed that, in his experience, when a person dives 

 under water, the eyelids open out. The deeper one goes the less light 

 is there in the water. Pebbles and other small objects at the bottom, 

 which appear magnified near the surface, diminish in apparent size 

 when the bottom is approached ; consequently, when the Seal dives after 

 his prey, his eyes need not alter, he thought, because the deeper he 

 goes after the objects of which he is in pursuit, the smaller they become ; 

 and he would require great visionary power if he were to dive much 

 deeper than a man can. 



Mr. "Wilson, in reply, said he believed the Seal's eye to be specially 

 adapted for the water. The animal took its prey in the water, and 

 therefore must be able to see best in that element. As to the density 

 of the lenses of his eye, he believed their refractive power to be altered 

 by the muscles, viz., the ciliary, assisted by the recti and other external 

 muscles; and he observed, that in the specimen of the Seal's eye, when 

 it was freshly removed from the head, the ciliary muscle was extremely 

 small. He submitted it to Dr. Eobert M'Donnell, who discovered no 

 voluntary muscular fibre in it. In the specimen in spirits, the ciliary 

 muscle and space were very large. 



The following paper was afterwards read : — 



Notes on Cottus Grgbnlandicus — the Greenland Bullhead. By 

 "William Andrews, Y. P., M. R. I. A. 



It is with much gratification that I have again the pleasure of sub- 

 mitting to the Society a beautiful specimen of* the Greenland Bullhead — 

 Cottus Grcenlandicus — and the more especially as it will remove the 

 doubts that probably may have been entertained with regard to its 

 actual capture on the Irish coast, and as to its identity with the New- 

 foundland species. 



I am indebted to the kind attention of my friend, Thomas Alexander 

 Montgomery, Esq., of Howth, for the handsome and richly-marked 

 specimen now before you. It was taken by line off the Pier of Howth, on 

 the 14th of December last ; and Mr. Montgomery, seeing its extreme 

 novelty, at once secured it. 



