THE STUEGEONS AND STURGEON INDUSTRIES. 255 
on their surfaces also become deeper and the lateral flattening of these organs is also 
more apparent in the adult. 
When the young sturgeon first leaves the egg there are no outward indications of 
the barbels. The anterior and inferior part of the head is bluntly rounded, and there 
is little or no indication externally of the presence of a suctorial disk such as is seen 
in the larvae of Lepidosteus, where this disk subsequently degenerates and is carried 
to the tip of the snout. This is well seen in the recently hatched larvae of the com- 
mon sturgeon figured in the appended plates. 
The barbels grow out a few days after hatching at a point just in front of the mouth 
as two pairs of short, blunt, fleshy processes on either sule of the median line, as 
shown in Figs. 54 and 55, p. 89, Vol. il, of Balfour’s Comparative Embryology, and in 
Figs. 14, 15, 16, and 17 on Plates XL and XLI of this paper. This blunted, cylindrical 
appearance of the barbels is retained until the young sturgeon has reached some 
size, as shown in Figs. 19, 20, and 21, of the young sterlet before the lateral plates 
of the body are much more than indicated and when the snout is beginning to become 
pointed and grow in length rapidly. The bases of both pairs are also more closely 
approximated during these early stages, though there is great variation in this respect 
even in different adult individuals, but in the latter the pairs never seem to arise from 
the same base as do the barbels in the very young fish. The barbels of the embryo 
of the sturgeon do not grow out so precociously as do those of the cat fish, as shown by 
the writer in Ictalurus albidiis, where they, moreover, have a cartilaginous supporting 
axis. This fact, as well as their tactile function in both cases, militates, it seems to me, 
strongly against the opinion that the barbels of fishes are necessarily derived from the 
papillae of a suctorial disk such as is found in the larvae of Lepidosteus. Besides, the 
late appearance of the barbels at the angle of the month in Cyprinus carpio, and of the 
chin barbels in Menticirrus, Gadus, Onos, etc., indicates a want of community of descent. 
Another epidermal system of sense organs extending over the under side of the 
snout of sturgeons both young and old is of interest, since it is probably a part of the 
system of tactile apparatus represented by the barbels. The structures now referred 
to are the depressed areolae found in front of the mouth, and divided partially in the 
median line by the roughened carina, formed by the produced parasphenoid bone, on 
the lower side of the snout, into a pair of triangles with their acute extremities 
directed forward. The small depressed areolae at the anterior part of this area are 
oblong ; back near the mouth they are nearly round, with irregular margins. Zograft’s 
results indicate that these areas are the points where sensory nerves terminate. My 
dissections indicate that their nerve supply comes from the most anterior branch of the 
fifth nerve. The position of these organs is such as to bring them into play as acces- 
sory to the barbels in seeking for food at the bottom of the estuaries where the stur- 
geon doubtless spends most of its time when feeding. 
7. THE LYMPHATICS OF THE STURGEON. 
The lymphatic system of the sturgeons is somewhat remarkably developed, and 
recalls in some respects that of the lampreys. In the lampreys, a stout triangular cord 
of lymphatic tissue overlies the spinal cord. This cord of lymphoid tissue, in those 
forms, is invested by the fibrous connective tissue which also invests the spinal canal 
as the dura mater and as the outermost fibrous covering of the notochord. It occu- 
