ZOOLOGY. 551 



in order, as it were, to play their parts in mutual con- 

 sent ; but so soon as the sense of feeling became indi- 

 vidualized into tactile organs, then also the eye made its 

 appearance in a detached or isolated manner. 



3342. The Fish's eye is upon the whole composed of 

 the same structures as in the Mammalia ; but it is devoid 

 of motion and external coverings. 



3343. The ear, as being the sense o motion, has 

 scarcely withdrawn itself from the brain, has not yet 

 become a true external organ, and that portion of it 

 which appears externally, is subservient to inferior sys- 

 tems, such as the branchiae or gills. 



3344. The external auditory organ has become con- 

 fluent with the branchial aperture, and the auditory 

 ossicles have become parts of the branchial operculum. 



3345. In the internal ear only the three semicircular 

 canals have been left. The cochlea is not yet developed. 



As true palpebraa or eyelids are wanting to the visual 

 organ, so also are the conchs of the external ear. 



3346. The nostrils exist, because a vertebral canal, 

 which terminates in them, is present ; stoutly-developed 

 olfactory nerves are also present, so that the sense of 

 smell cannot be wanting. Only this sense has not yet taken 

 the respiratory organ into communication with itself, 

 and both therefore live for themselves in an arrested or 

 stunted condition. This nasal organ does not open 

 into the mouth, admits of neither water nor air passing 

 through it, and therefore serves not as a test-organ to the 

 respiratory process. This is my main point for distinction 

 of Fishes from Reptiles. 



3347. Every Sarcozoon, whose nostrils do not open 

 into the mouth, is a Fish. The Siren therefore does not 

 belong to the present class, while the Lepidosiren, having 

 an imperf orate nasal organ, does, 



3348. The tongue has remained rather an organ of 

 touch and deglutition, than an instrument of taste. The 

 salivary glands are scarcely developed. 



3349. But the tongue here appears for the first time 

 in the animal kingdom as a perfect organ provided with 



