340 FISHES. 



remote from the centre, and most frequently penetrates it obliquely. 

 After having penetrated the sclerotic, it frequently makes a long 

 furrow througli 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 very 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 retini is easily divided into two 

 kminfe, 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, Ave 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 proba])le 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 back 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 liis Pentesteseion, page 224, contains a tolerabls drawing of the serai- 

 circular canals, and patrons 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 Swammerdam, (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 1737. 



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 historioe piscium pronwvendi-e, printed in 1740, 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, marenic, her- 

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

 plaice, barbel, and several other cyprius, &c., but entirely independent of their 

 position and their connexion with the labyrinth. 



In 1/53 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- 



