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 im 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 numbeg of incisions, the 
denticulations of one space corresponding exactly to those of the 
adjoming, so that in no part can any yoid 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 mdependent 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, Ist, 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 strize m 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. 
