340 FISHES. 



remote from the centre, and most frequ«ntly penetrates it obliquely. 

 After having penetrated the sclerotic, it frequently makes a long 

 furrow through the greasy tissue and between the branches of the 

 vascular tissue, before penetrating the choroid and the ruyschian. 

 Its diameter shrinks considerably when it enters the ruyschian ; some- 

 times it appears at the interior of the eye as a white, and round or 

 irregular spot, and sometimes as a line. When the nerve is folded, 

 the retina itself has its internal lamina veiy much folded ; it lines, 

 moreover, as is common, all the interior concavity of the eye as far 

 as the origin of the uvea, and envelops also almost all the vitreous. 

 In those fishes which have a falciform ligament, it is cleft to allow it 

 to pass, but it very closely contracts, and its fissure is frequently 

 marked by two whitish lines which follow on this side the whole of 

 the concavity of the eye. The retina is easily divided into two 

 laminae, the internal of which is thinner and more fibrous, and the 

 external more pulpy. 



From this general structure of the eye of fishes, the nearly com- 

 plete spheroidal character of its crystalline, the immobility of its pupil, 

 the difficulty there is in it of varying the length of its axis, we can 

 have no doubt that their faculty of seeing is very imperfect. Images 

 can be only confusedly painted upon their retina; and consequently 

 it is not probable that they are susceptible of distinct perceptions of 

 the forms of objects. It is nevertheless certain that they discover 

 their prey even at a great distance, and that they know it by seeing 

 it, since artificial flies deceive them, and cause them to bite the hook 

 as if they were real baits. 



The Ear*. 



The ear of fishes consists in some measure only of the labyrinth, 

 and moreover a labyrinth less complicated in many respects than 

 that of quadrupeds and birds. 



* As far hack as 1600, and 1610, Casserius had examined many important parts 

 of the ear of fishes, and was better acquainted with it, than with the same organ in 

 man ; for his Pentesteseion, page 224, contains a tolerable drawing of the semi- 

 circular canals, and petrous bones of the pike. 



In the Acta Medica of Copenhagen, for the year 1673, Stenow gives an abridged 

 description of the internal ear of the mustelus, which, though unaccompanied by a 

 drawing, is tolerably exact. 



It may also be inferred from certain expressions of Swammerdain, (Bibb. Nat., 

 vol. 1. p. iii.) that the labyrinth of fishes was not unknown to him. But his book 

 was not printed till after his death in 1 737. 



It is also said that Duvernay was aware of it ; but his observations on this sub- 

 ject have never been published. 



Bromel, Professor Upsal, has given a catalogue of the stones of the ear of fishes 

 which he had collected. 



Klein, in his first Missus historic? pisrivm promorendee, printed in 1 740, speaks in 

 detail of those stones, and gives correct drawings of them, though not in situation 

 or in connexion with the labyrinth, in the pike, salmon, trout, ombre, marenje, her- 

 ring, cod, dorsch, lote, sandre, perch, the acerina, the gasterosteus, the turbot, 

 plaice, barbel, and several other eyprins, &C., but entirely independent of their 

 position and their connexion with the labyrinth. 



In 1753 Etienne Louis Geoffroy, a Physician of Paris, presented to the Academy 

 a memoir ex professo, on the ear of fishes which was not printed till 1 778. It con- 



