Royal Society. 47 



vering, to enable it to climb rocky ground without stumbling. 

 Its long neck consists of only seven bones, being the same 

 number that occurs in the human skeleton. The tongue is 

 every where smooth and slightly adhesive ; it is spotted, but 

 the spots are not raised. Its favourite food is the Acacia tree, 

 of that species now called Acacia Xariffa : it has a pleasant 

 flavour both boiled and raw, and its twigs are succulent. The 

 tongue being much exposed to the sun, has a black rete mu- 

 cosum, to prevent blistering. Drawings, by Mr. Cross, ex- 

 hibit the mode in which it lays hold of the branches of trees. 

 It drinks milk, first rinsing out its mouth with a portion, and 

 rejecting that so employed. It chews the cud, its body being 

 then recumbent and its head and neck erect* 



The organ of vision of the Cobitis anableps is very remark- 

 able. The specimens examined by the author were furnished 

 by Dr. Muttlebury, of Bath. He first exposes the errors of 

 Artedi and his followers, in their description of this animal ; 

 and states, that the cornea being removed, the iris is exposed, 

 having an appearance of two pupils; but on more accurate ex- 

 amination this effect is seen to arise from two lateral project- 

 ing portions, folding over each other in the middle, thus di- 

 viding the aperture into two. They do not however unite; 

 and in some specimens they leave the pupil entire, only very 

 narrow in the middle, forming an oval, broad above and nar- 

 row below ; usually, however, they leave two distinct aper- 

 tures. The crystalline, instead of being spherical, is not even 

 circular, having a small projection at the lower edge, directly 

 behind the smaller aperture. When examined in the micro- 

 scope, a small bundle of muscular fibres is seen coming from 

 the capsules of the vitreous humour in the lower part, and en- 

 tering that of the crystalline just at the disc where the smaller 

 curve joins the large one, the action of which is to bring the 

 lower mammary process of the lens downwards and backwards 

 into the centre of the lower apertures in the iris; thus con- 

 stituting a complete organ for vision at near distances, inde- 

 pendent of the part of the lens opposed to that large aperture, 

 which is destined for more distant objects. 



The author regards this structure as destined to a similar 

 purpose with that of the marsupium in birds, viz. to obviate 

 a difficulty arising from a want of motion in one direction in 

 the eye-ball. He considers that by its means also, the fish, 

 when lying with its eye-ball above the surface of the water, 

 may enjoy distinct vision both in air and water by the motions 

 of the crystalline and eye-ball, combined with the adapting 

 power of the two apertures of the iris to a circular form. 



A paper was read, entitled, H Experiments to determine the 



difference 



