550 BIOLOGY. 



stantly in the water. The whole skin is undermined by 

 mucous canals and perforated by their excretory aper- 

 tures. These foramina of the lateral line are arrested, 

 and metamorphosed branchial foramina, which have only 

 retained the evaporative function of respiration. 



3336. The remnants of the tegument's annulation 

 are the scales. They are desiccated air-branchiae, 

 alary opercula or elytra, and consequently indicate that 

 feature of the Insect, which has continued to work its way 

 into the class of Fishes. 



3337. Like the skin, so are the limbs tegumental 

 members. What is flesh and bone upon them, has kept 

 quite close to the body, and that only which is designed 

 for splitting into digits projects, constituting tegumental 

 digits with cartilages -fins. These fins are something 

 better than the lateral papillae of the Worms, are 

 furnished at their base with joints, and are in number 

 only four, but crippled or stunted in every possible way. 



3338. The fin-rays do not correspond to the digits, 

 but to the nails. They are fibrillated nails, like the 

 wing-feathers of Birds. 



3339. Lastly, the head possesses all the organs of 

 sense which belong to a head, but they are still far 

 removed from their perfect condition. 



3340. As the nervous system is the first mass, from 

 which the remaining ones have been set free, so also is 

 the nervous sense the first after that of the tegument, 

 which appears as a whole, and serves as a pattern for the 

 subsequent senses. The eye is the sense which is first 

 developed most perfectly, not directly as regards its own 

 completeness, but when considered in reference to the 

 others. 



As the sense of feeling has been at once manifested in 

 the vegetative animals as a peripheric nervous sense ; so 

 antithetically or vice versa it is in the higher animals the 

 light-sense, as being the central nervose sense, which 

 appears. 



3341. Hitherto both these senses stood altogether 

 alone with each other upon the stage of animal existence, 





