208 CLASSIFICATION OF THE ANIMAL, KINGDOM. 



the Vertebrate world, which is not found in lower animals, the lymphatic 

 tubes, which absorb the nutritious articles of food, and pour them into the 

 larger veins to be mixed up with the blood. Some fishes are also provided 

 with large swimming bladders, which enable them to float or sink at pleasure. 

 The circulation of their blood, which is of a red colour, is carried on by 

 means of a heart, composed of a single auricle and ventricle, situated beneath 

 the branchial organs, but it is not purely of a systemic character. 



The eyes of fishes are much more highly developed that anything we 

 have met with in the lower kingdoms, but do not yet attain the perfection 

 of these organs in terrestrial vertebrata. Their sense of hearing is still 

 very imperfect, and, although superior, is still analogous to that of the 

 Cephalopods. Their organs of smelling are also of a very simple structure, 

 the nostrils not communicating with the mouth, but being merely two blind 

 sacs, and their power of taste must necessarily, on account of the continual 

 exposure to the fluid in which they exist, be of a not very discriminating 

 character. As regards their means of reproduction, these organs in both 

 male and female are still of a simple form, especially in the osseous genera, 

 the cartilaginous fishes being more highly organized in this respect, and 

 being provided with a more complex apparatus. The number of eggs in 

 some fishes is most wonderful, but in others, as the destructive shark 

 and those of the cartilaginous class, providentially they are much less 

 numerous, and are concealed in singular bags of a horny texture, well 

 known to all sea-side ramblers under the name of skates' barrows. 



Some fishes are viviparous. Lastly, with regard to the nervous system 

 of fishes, we find it very considerably enlarged, according to the vertebrate 

 type, and in proportion to their high organic development. The principal 

 portion, the analogue of the supra-cesophagal ganglion of lower animals, 

 is a large mass situated within the head, called the brain. Though now 

 so concentrated and enlarged, and corresponding in character with that of 

 Terrestrial Vertebrata to a certain extent, yet it still preserves the old 

 ganglionic structure; for, besides that portion called the cerebral hemisphere, 

 the seat of the mental powers in vertebrate animals, and the cerebellum, 

 it is divided into large lobes, which communicate with the different regions 

 of the senses, and other parts of the head and stomach, and from this 

 encephalon proceeds a long chain of nervous cords right down the whole 

 length of the spine, being protected by the superior spinous processes of 

 the vertebrae. From all the principal masses are given off threads, which 

 traverse, and, as it were, animate the whole system, wherever in fact, 

 any power, be it sentient or muscular, is exercised in the highly-organized 

 families of the Vertebrate division ; there we find a corresponding adequate 

 system of nerves guiding and directing each process and function of life. 



The next great class, that of Ecptiles, includes animals of very diver- 



