456 THE STURGEON. 
that a brief description must be given. The front portion, which starts 
immediately below the eye, is called the “ prazoperculum,” and immediately 
behind it comes the “ operculum.” Below the latter is another piece, termed 
from its position the “sub-operculum, ” and the lowest piece, which touches 
all the three above it, is called the “inter-operculum.” Below the chin and 
reaching to the sub-operculum, are the slender bones, termed the “ branchi- 
ostegous rays,” which differ in shape and number according to the kind of 
Fish. 
The scales with which most of the Fish are covered are very beautiful in 
structure, and are formed by successive laminz, increasing therefore in size 
according to the age of the Fish. They are attached to the skin by one 
edge, and they overlap each other in such a manner as to allow the creature 
to pass through the water with the least possible resistance. The precise 
mode of overlapping varies materially in different genera. Along each side 
of the Fish runs a series of pores, through which passes a mucous secretion 
formed in some glands beneath. Iu order to permit this secretion to reach 
the outer surface of the body, each scale upon the row which comes upon the 
pores is pierced with a little tubular aperture, which is very perceptible on the 
exterior, and constitutes the “lateral line.” The shape and position of this 
line are also used in determining the precise position held by any species. 
In comparing the scales taken from different Fishes, it is always better to 
take those from the lateral line. 
The heart of the Fish is very simple, consisting of two chambers only, one 
auricle and one ventricle. The blood is in consequence cold. 
The hearing of Fishes appears in most cases to be dull, and some persons 
have asserted that they are totally destitute of this faculty. It is now, how- 
ever, known that many species have been proved capable of hearing sounds, 
and that carp and other fish can be taught to come for their food at the 
sound of a bell or whistle. The internal structure of the ear is moderately 
developed, and there are some curious little bones found within the cavity, 
technically called the otoliths. 
THE fishes comprised in the first order are called by the rather harshly 
sounding title of Chondropterygii, a term derived from two Greek words, the 
former signifying “ cartilage” and the latter “a fin,’ and given to these crea- 
tures because their bones contain a very large amount of cartilaginous sub- 
stance, and are consequently soft and flexible. The bones of the head are 
rather harder than those of the body and fins. 
The first family, of which the common STURGEON is a good and familiar 
example, is at once known by the cartilaginous or bony shields with which 
the head and body are at intervals covered. 
In this remarkable fish the mouth is placed well under the head, and in 
fact seems to be set almost in the throat, the long snout appearing to be 
entirely a superfluous ornament. The mouth projects downwards like a 
short and wide tube, much wider than long, and on looking into this tube no 
teeth are to be seen. Between the mouth and the extremity of the snout 1s 
a row of fleshy finger-like appendages, four in number, and apparently 
organs of touch. 
One or two species of Sturgeon are important in commerce, as two 
valuable articles, namely, isinglass and caviare, are made from them. The 
former substance is too well known to need a description, and the mode of 
preparing it for use is briefly as follows. The air-bladder is removed from 
the fish, washed carefully in fresh water, and then hung up in the air for a 
day or two, so as to stiffen. The outer coat or membrane is then peeled off, 
and the remainder is cut up into strips of gre iter or lesser length, technically 
galled stuples, the long staples being the most valuable. This substance 
