292 M. Krohn on the Anatomy and 



not seem adapted for swimming. Probably they facilitate the 

 suspension of the animal in the water by increasing the extent of 

 surface of the body. 



I now proceed to consider the internal structure. I shall 

 commence by that of the teguments and of the subjacent fibrous 

 layer lying beneath : I shall then pass in review the organization 

 of the three sections of the body, the head, trunk, and tail*. 

 The study of the nervous system, followed by that of the eye, 

 will conclude our remarks on this animal. 



Teguments. — With the exception of the head, the skin is 

 throughout, proportionally speaking, coriaceous and thick ; it is at 

 the same time smooth, and scarcely loses its transparency. When 

 immersed in spirits of wine, an epidermis appears to separate from 

 it ; it is completely homogeneous and presents no peculiar ele- 

 mentary tissue. On animals which have been kept for some time 

 in alcohol, a great number of isolated, white, opake, and clearly 

 circumscribed spots are discernible ; these are probably mucous 

 follicles, more numerous and more pressed together on the ante- 

 rior part of the trunk. On examining the internal surface of the 

 skin, peculiar delineations, the nature of which I could not ascer- 

 tain, are easily discernible with a moderate magnifying power. 

 They are very clearly distinguishable on the lateral surfaces of 

 the trunk, where, as I shall observe presently, there exists no 

 subjacent muscular layer. With a higher power, these designs 

 appear to traverse a number of fields, the outline of which is 

 serrated in a zigzag manner by a large number of incisions, the 

 denticulations of one space corresponding exactly to those of the 

 adjoining, so that in no part can any void be perceived. At 

 several points, very little extended, polygonal cells may be de- 

 tected, often very regular, and presenting a central nucleus. 

 Neither these cells nor the nuclei form any independent layer 

 which can be isolated from the skin. 



Fins. — As the fins are intimately blended at their base with 

 the skin, the description of their structure will best follow here. 

 They are formed, 1st, of a fundamental very transparent sub- 

 stance, which does not in the least become opake in spirits of 

 wine, and presents no trace of either cells or fibres ; and 2ndly, of 

 a peculiar envelope, of the elementary structure of which the mi- 

 croscope may furnish some indications. Even with the naked eye, 

 loosened strise in the form of rays, directed from the base to the 

 margin of the fins, are distinguished; but, viewed thus, it is a very 

 coarse image compared with that which it presents under the 

 microscope. A number of very elongated, flexuous and delicate 



• Every one will immediately understand that the division of the body 

 into trunk and tail is arbitrary, and that the only advantage it has, is its 

 being convenient and clear. 



