HAUGHTON REMAKES ON THE EYE OF THE SEAL. 221 



backwards. All the authorities are agreed that, when we look at a 

 near object, we shorten the eye by muscular exertion. Tn the eyes of 

 different animals the structure of the external muscles varied in every 

 possible way ; and there was an equally great variety in the structure 

 of the external case. In birds there was also an arrangement not unlike 

 that occurring in the Seal, viz., a second cup, set face to face with the 

 posterior one, and at the point where the anterior thickening of the sclero- 

 tic occurred. He would ask Dr. Wilson what he supposed to be the 

 function of the ciliary muscle in the Seal's eye, or whether he consi- 

 dered that the Seal possessed a ciliary muscle at all. 



The President said, "the question was far from being merely an ana- 

 tomical one. Anatomists had examined the eyes of animals with respect 

 to the mechanism of accommodation, but seemed to have got no definite 

 result, as far as he could understand. Opticians had also examined the 

 eyes of animals with reference to the same question, without much 

 result. None of them singly had arrived at results of much value. 

 The true state of the case was to be arrived at by a combination of 

 the researches of both. It appeared to him that the first difficulty 

 about the question was, to settle a point which naturalists only can de- 

 cide, namely, whether the Seal can see better in water or in air. 

 The difficulty raised by Dr. Bennett is removed the moment we assume 

 that the Seal sees better in water than in air. If it be assumed, on the 

 contrary, that the animal sees best in air, opticians and anatomists must 

 provide a mode of elongating his eye. If the Seal see best in water, 

 there must be a power of accommodation in the eye, and it must be 

 shortened when he comes into the air ; and that hypothesis would fall 

 in with Dr. Bennett's objection, that the action of the muscles would 

 shorten the globe of the eye, and not elongate it. Whether the action 

 of the muscles of the Seal's eye is to shorten or to elongate the globe must 

 be decided by anatomists, but that will not interfere with the settlement 

 of the point as to the nature of the accommodation in the Seal's eye. 

 The great interest attaching to the problem as to the eye of that animal, 

 more than that of any other, depends upon the fact, as admitted by na- 

 turalists, that he sees very well in air, and also very well in water. He 

 will dip at the flash of a gun before the bullet can reach him ; and it is 

 equally certain that he must see well in water, because he can catch 

 the salmon. Therefore, both opticians and anatomists must start from 

 the hypothesis that he sees equally well in both elements. The change 

 in refractive conditions that the animal must be capable of in passing 

 from one of these elements to the other is something very remarkable. 

 Anatomical inquirers speak at their ease about the lengthening of the 

 Seal's eye, the changing of the cornea, and the alteration in the shape 

 of the crystalline lens. He did not think they had considered the 

 amount of change that the necessity of the case would require. He 

 made some calculations himself, which ho checked by a reference to the 

 work published by a gentleman who was a much higher authority on 

 the subject of optics than he was, namely, Dr. Lloyd, the Vice-Provost 



