SEAL. 



637 



have to use the eyes deep in the water, and when 

 there is very little light, or indeed none, or next to 

 none, as when the surface is very much roughened, 

 or covered by ice with snow over it, which last must 

 exclude the light. Yet the seals do not hybernate at 

 those times, even in the long night of the arctic 

 winter ; for they are careful to keep breathing-holes 

 in the ice, and, while an animal continues to breathe, 

 it must also eat. 



While the eyes of the whales are remarkably small 

 for the size of the animals, those of the seals are very 

 large. In this they follow a very general law among 

 animals, whatever may be the element in which they 

 live. If they depend chiefly upon the eye, and 

 especially if they are feeders in the night, or in 

 places to which little light can come, we invariably 

 lind that the}' have the eyes very large. This is the 

 case with owls, and other nocturnal birds, and also 

 with those nocturnal mammalia which find their 

 food chiefly by sight. It holds even in the sea. The 

 surface-fishes usually have the eyes small ; and they 

 get gradually larger and larger, till, when we come to 

 those which inhabit the deeps, and yet are active, 

 feeding upon other fishe?, their eyes are very large, 

 of which we have an example in the stargazers. It 

 must not be understood that we mean to say that the 

 large eye has the sense of vision in greater perfection 

 than the small eye, for sensation is not a quality of 

 matter, but a function of life, and therefore the acute- 

 ness of it has nothing to do with the size of an organ ; 

 and we find that, in equal lights, if they be strong 

 ones, the small eye has the better of the large one, 

 especially in the power of enduring a continued 

 exposure to the light. But in faint lights the large 

 eye has a greater field of view, and thus finds the 

 object more readily than a small one does, and it also 

 admits more light. The large eyes of the seals, 

 therefore, are well adapted to the imperfect light in 

 which they have to find their food. 



The eyes are placed very near to each other, and 

 thus they indicate that the animals follow their prey 

 upon the forward view, as is done by the nocturnal 

 quadrumana, which also have the eyes very near to 

 each other. The form of the eye-ball is nearly sphe- 

 rical, the vertical diameter in the common seal being 

 an inch and a half, and the horizontal diameter an 

 inch and a third. This is in accordance with the 

 form and actiun of the pupil, which closes to a vertical 

 line. The sclerotic coat of the eye is composed of a 

 nbro-cartilaginous membrane of considerable thick- 

 ness, very hard and firm in the fore part round the 

 cornea of the eye, and also in the posterior portion, 

 but soft and rather flexible in the part intermediate 

 between them. The structure of the coat, which may 

 be considered as forming the basis of the eye, is 

 peculiar ; Blumenbach and some others have sup- 

 posed, and certainly with much probability of being 

 correct, that the flexibility of the central zone of the 

 sclerotic admits of an adjustment of the focus of the 

 eye, by means of which the animal can see equally 

 well in the water and in the air. The cornea of the 

 eye is flat, like those of the eyes of most aquatic 

 animals, there being less distinction of light from a 

 flat cornea than from a convex one of the same 

 surface. This cornea is about three quarters of an 

 inch in diameter, and thicker at the sides than in the 

 middle. The crystalline lens is spherical, like that 

 of fishes, and about half an inch in diameter. All the 

 parts of the eye are, indeed, very well formed, and 



the muscles with which it is supplied are of consider- 

 able power. The lachrymal gland is very small, as 

 the eye does not require to be lubricated with the 

 secretion of this gland when the seal is in the water. 

 From its equal adaptation to the air and the water, 

 the eye of the seal is an important one by means of 

 which to study the physiology of eyes generally, but 

 our limits will not permit us to pursue it farther. 

 We shall therefore cast just a passing glance on 

 the geographical distribution of these most curious 

 animals. 



There is no sea on the surface of the globe in which 

 seals are not to be met with, not in the breadth of 

 the great oceans indeed between the shores, though 

 they are capable of taking journeys of considerable 

 length. They are no where so abundant as on the 

 shores of the dreary lands in the high latitudes, and 

 near the margins of the ice ; and in the north they 

 form an important article in the domestic economy of 

 the inhabitants of those inhospitable climates. In the 

 equatorial seas the seals are solitary, or seen at the 

 most in pairs. In the temperate latitudes they as. 

 semble in groups, but not in very large numbers ; but 

 in the high latitudes of both the north and the south, 

 the herds of them are so numerous, beyond all count- 

 ing, that the most active fishing can hardly have any 

 effect in thinning their numbers. Though they are 

 less known in the high latitudes of the southern hemi- 

 sphere than in those of the northern, it is probable 

 that, taking all the longitudes into account, they are 

 upon the whole more numerous, as they have the 

 complete range of the parallel, which is not the case 

 in any latitude of the north. Those of the three 

 great divisions of the sea are chiefly different from 

 each other, and they have been employed as the basis 

 of a popular mode of division, which has the advan- 

 tage of connecting the species with their habitats, 

 without any formal description. There are the seals 

 of the North Atlantic, the seals of the North Pacific, 

 and the seals of the South Seas ; among which latter 

 there are of course no longitudinal distinctions, as 

 there are no lands to separate the seas from each 

 other, and give them and their productions different 

 characters, as is the case with the North Atlantic and 

 the North Pacific, where the great current in the 

 north parting the former, and the comparatively small 

 one in the latter, give quite a different character, and 

 bring the arctic winter farther to the south in the 

 Pacific than in the Atlantic. 



In all the seas in which they are found, the seals 

 frequent the shores only at a certain season of the 

 year, and appear to disperse themselves more gene- 

 rally over the waters during the remaining portion of 

 it, which is usually much longer than that in which 

 they throng to the shores. Those of the south resort 

 chiefly to the dreary and inhospitable isles which lie 

 off the southern extremity of the American continent, 

 though they also come in considerable numbers to 

 the shore, especially the south-west, which is much 

 broken by inlets of water and little isles with chan- 

 nels between. The south of Africa is rather warm 

 for their coming to it in any considerable numbers ; 

 but they resort in formidable array to the south part 

 of Australia, and especially to Bass's Strait, where 

 the islands are favourable for their basking, and fish 

 are abundant for their food. In the northern seas 

 they resort to the shores generally in the high lati- 

 tudes ; but there also they prefer the islands to the 

 mainland. Among the Aleutian islands, and in all the 



