DISTINCTIVE CHARACTER OF ANIMALS. ' 183 



LECTURE II. 



ON ZOOLOGICAL SYSTEMS, AND THE DISTINCTIVE CHARACTERS OF ANIMALS. 

 (The subject continued.) 



In our last lecture we took a momentary glance at the history of zoology 

 as a science, noticed the primary features of the best methodical arrange- 

 ments to which it has given rise, and made some progress towards a brief 

 delineation of that of Linnaeus, which still takes the lead amid the writers 

 of the present day, and is hence chiefly entitled to attention in a course of 

 popular study, generally collating it, however, with that of M. Cuvier, as we 

 proceeded. 



We observed that the Linnsean system comprehends all animals of every 

 description whatever, under the six classes of mammals, birds, amphibials, 

 fishes, insects, and worms. We pursued this arrangement in an ascending 

 scale, as most consistent with the plan adopted at the opening of the present 

 course of instruction ; and commencing with the class of worms, finished 

 with that of insects. It remains for us to prosecute the same rapid outline of 

 inquiry through the four unexamined classes of fishes, amphibials, birds, and 

 mammals. 



Fishes are classically characterized in the Linnaean system as being always 

 inhabitants of the water ; swift in their motion, and voracious in their appe- 

 tite ; breathing by means of gills, which are generally united by a bony arch; 

 swimming by means of radiate fins, and for the most part covered over with 

 cartilaginous scales. 



The class is divided into six orders ; the ordinal characters being taken 

 from the position of the ventral or belly fins, or from the substance of the 

 gills. The orders are, apodal, fishes containing no ventral or belly fins ; 

 jugular, having the ventral fins before the pectoral ; thoracic, having the 

 ventral fins under the pectoral ; abdominal, having the ventral fins behind the 

 pectoral. In all these four, the rays or divisions of the gills are bony. In 

 the fifth order, which is called branchiostegous, the gills are destitute of bony 

 rays ; and in the sixth, or chondropterygious order, the gills are cartilagi- 

 nous ; all which will be easiest explained by a few familiar examples. Into 

 the general divisions of this class M. Cuvier has introduced no change of any 

 importance whatever, his own sections and names running parallel with those 

 of Linnaeus. 



The kind best calculated to elucidate the first or apodal order, is the well 

 known muraena or eel; since every one must have noticed, that this fish has 

 no ventral or, indeed, under-fins of any kind. In many of its species, it has 

 a very near approach to the serpent tribes ; insomuch that several of them 

 are called sea-serpents, and by some naturalists are described as branches of 

 the serpent genus. Even our own common eel, muraena Anguilla, is often 

 observed to quit its proper element during the night, and, like the snake, to 

 wander over the meadows in search of snails and worms. 



The next genus I shall mention is the gymnotus, of which one species, 

 gymnotus electricus, is the electric eel, an inhabitant of the rivers of 

 South America, from three to four feet long, and peculiarly distinguished by 

 its power of inflicting an electrical shock, so severe as to benumb the limbs 

 of those that are exposed to it. The shock is equally inflicted whether the 

 fish be touched by the naked hand, or by a long stick. It is by this extraor- 

 dinary power, which it employs alike defensively and offensively, that the 

 electric eel escapes from the jaws of larger fishes, and is enabled to seize 

 various smaller fishes as food for its own use. There are, however, a few 

 other fishes, as we shall have occasion to notice in proceeding, that possess a 

 similar power, as the torpedo of European seas, and especially of the Medi- 

 terranean, and the electric silurus of those of Africa. 



