CHRYSALIS. 



moveable; and as they are generally in several 

 rows, they can hold on with one part, and cut and 

 tear with another ; and if we except those fishes 

 which feed upon Crustacea or sea-weed, they are per- 

 haps the only ones which divide their food by the 

 action of the mouth. 



The skin is a very important part of the structure 

 of these fishes, and may be said to contribute almost 

 as much to support them in their motions as the bony 

 part of their structure. Indeed the skin is almost 

 the only part in which any substance approaching to 

 the character of bone is formed. Some of them pro- 

 duce large plates as in the sturgeons (see the article 

 ACCIPENSER), others hooks and spines, some of which 

 are very formidable weapons, and others tubercles of 

 various forms and sizes. The various species of sha- 

 green which is used for covering boxes and various 

 other articles are the skins of sharks. These bony 

 appendages are exceedingly hard in their consistency ; 

 but whatever may be their form, they partake of the 

 general character, which \ve have already alluded to 

 as distinguishing the internal bones they do not 

 exhibit a fibrous structure, but are uniform throughout; 

 and though it is difficult to divide them in any parti- 

 cular direction, they are equally divisible in all. These 

 fishes are divided into two sub-orders, those which have 

 the gills fixed, and those which have the gills free. 



WITH FIXED GILLS. In these the gills adhere 

 to the skin, or rather to the integument of the sac in 

 which they are contained, instead of being loose at 

 their posterior edges, as is the case with other fishes. 

 The water does not therefore pass through the gills 

 of these fishes as it does through those of others; 

 neither have they any gill-lid, or operculum, by the 

 action of which they carry on the operation of 

 breathing. They have between every two fringes 

 or leaves of the gills, an opening for the admission 

 of water, and the outer edge of each gill is supported 

 by a cartilaginous arch imbedded ia the flesh, between 

 the openings ; and it is by means of the muscles 

 acting on this arch, that the process of breathing, 

 which is a very slow one, is carried on. The genera 

 and species of this order are much more numerous 

 than those with free gills. They consist of two 

 families, PLAGIOSTOMUS, "oblique mouth," or "cross 

 mouth," the mouth being in the form of a slit under 

 the snout, which generally projects a considerable 

 way in front of the opening, arid the mouth, from 

 the absence of jaw-bones, admits of a great deal of 

 motion; and CYCLOSTOMUS, "round mouth," from 

 the mouth being in the form of a sucker, or capable 

 of turning backwards so as to be on the same plane 

 all round. Some notice of each of these families will 

 be given under its name in the order of the alphabet. 



WITH FREE GILLS. These have their gills free 

 at the one extremity, as is the case in ordinary fishes, 

 and they have only a single gill opening, for allowing 

 the water to escape. This opening is furnished with 

 a gill lid; but without any flap. This sub-order 

 consists of four genera, though all these may be in- 

 cluded in one family, the sturgeon family. See 

 STURIONID^:. 



Of these two orders or sub-orders, those with fixed 

 gills may be considered as the most typical ; but both 

 stand so distinct from the rest of fishes, that, with 

 the exception of the partial resemblance to plectog- 

 nathes above alluded to, they must be considered as 

 forming, not a subdivision of fishes considered as one 

 class of animals, but as a distinct class of fishes, which 



hold a very peculiar place in the structural system of 

 animals, and also from their numbers perform an im- 

 portant part in the living economy of the waters. 

 We must not suppose that there is any thing out ot 

 nature, in there thus being two distinct classes of 

 vertebrated inhabitants of the waters, any more than 

 that there should be different species ; for we have a 

 similar division of mammalia ; the marsupial animals 

 being as distinct from the other mammalia, as the 

 chondropterygii are from the other fishes. We have 

 mentioned that there are some points of relation be- 

 tween those second classes of mammalia and of fishes, 

 and one would be almost led to believe that they 

 are portions of a different creation from the other 

 classes, which they resemble in their common eco- 

 nomy and habits. It is exceedingly difficult, however, 

 to trace the analogies between sea and land animals, 

 not only from the great ignorance in which we must 

 for ever remain as to the details of what goes on in 

 the deep, but because many links in the chain are 

 wanting. 



CHRYSALIS or AURELIA. Under these terms 

 is designated the pupa state of lepidopterous insects. 

 Having already, in our article AURELIA, given some 

 account of the cause of the application of these terms 

 to this state, and in one article, BUTTERFLY, detailed 

 the peculiarities of the chrysalides of the Papilumida>, 

 we shall here briefly notice some general circum- 

 stances relative to chrysalides in general, and to 

 those of moths and hawk-moths in particular, reserv- 

 ing to the article COCOON our account of the con- 

 struction of those curious envelopes in which the 

 insect is often in this state inclosed. 



The pupa) of lepidopterous insects entirely differ 

 from those of every other order of insects, a circum- 

 stance of some interest as well as peculiarity, since in 

 other instances we find the pupae of several orders 

 exhibiting the same general form. In the Lepido- 

 ptera, however, the various organs of motion of the 

 future insect are laid along the breast and sides, but. 

 are folded up under a hard skin, whence they are 

 much less distinctly perceptible than in the pupae of 

 other insects. Linnaeus has termed this an obtected 

 pupa. In general lepidopterous chrysalides are of 

 an oblong-oval form, obtuse at the head, and gra- 

 dually becoming narrow towards the tail ; but in 

 some moihs, as in the Hornby* luna, the form is 

 shorter, and obtuse at each end. Under this form 

 the insect appears neither to have legs nor wings, it 

 seems even destitute of life, taking no nourishment 

 and appearing like an unorganised mass, the only 

 sign of life being a slight occasional twitching of the 

 hind part of the body. The outer covering appears 

 of a cartilaginous nature ; it is commonly smooth, 

 but in some few instances it is hairy. From the blunt 

 extremity of the body are to be observed various 

 small and narrow compartments, arranged like the 

 bands of a mummy. These are the coverings of the 

 legs and antenna?, disposed along the breast, the part 

 from whence they seem to arise is the head, which 

 is covered by a piece termed the Ccphalothcca. On 

 the outside of these narrow bands are to be observed 

 two broader scales, which, covering the wings, are 

 termed Pterotheca, arising from the opposite side to 

 the breast, and which is the covering of the thorax, 

 or Cytotheca. This is followed by the abdomen-case, 

 Gastrotheca. 



The chrysalis, upon quitting the exuvia of the 

 caterpillar, is soft and tender ; by degrees, however, 



