DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 735 
Kinestry and Conn refer very briefly to what they style a “neurenteric canal,” of 
which they give a figure (No. 78, fig. 30, pl. xv.). RArrar.E also recently alluded to it 
in Uranoscopus (op. cit., p. 28). That it has been rarely observed, and never fully 
described, is probably due to its evanescent character, and it may in some cases, indeed, 
never be developed. Batrour and Detauron (No. 19, p. 185) speak of it as “ that 
most variable structure in the chick,” and the same description may be applied to 
it in the Teleostean ovum. This canal can hardly be due to the supposed process of 
concrescence, as it has not the character so much of a vertical fissure as a depressed cavity 
passing obliquely downward and forward between the embryo and the yolk, and is best 
seen in transverse or side view. It is, indeed, less of a tubular canal than of a tranverse 
fissure between the convex embryonic surface and the concave yolk-surface, and opening 
externally by the blastopore. In PI. III. fig. 8, in the living condition its course is 
clearly indicated, the shallow dorsal groove continuous with the blastopore indenting 
the caudal region, and then merging in the descending tract, nec, which widens out and 
becomes lost in the mass of periblastic protoplasm, kv, in which Kupffer’s vesicle 
makes its appearance. Sometimes this neurenteric passage connecting the neuro- 
chordal groove above and the enteric region below is a distinct interspace (Pl. III. fig. 
9, and possibly nec? Pl. IV. fig. 5d). It is often marked by granules (Pl. III. fig. 
22), or even a tract of undifferentiated protoplasm, in which two or three clear spheres 
are imbedded (PI. III. fig. 20). Fig. 8, Pl. ILI., for instance, showed this last named 
condition at 10 a.M., with a connecting tract opening externally between the closing lips 
of the blastopore. An hour and a half later, a spindle-shaped plug (PI. IIL. fig. 8a) 
sending outward an acuminate process, interrupted the canal, nec, and presented 
amceboid movements. The plug then coalesced with the margin of the blastopore, and, 
assuming a distinctly granular appearance, formed a bridge across the fissure connected 
with the inferior tract (fig. 8c).* Meanwhile, the clear vesicles mentioned above had 
enlarged, and finally coalesced to form Kuprrer’s well-known structure. Such a plug 
as we have described BaLrour and Dertcuron noted in the chick, and they speak of a 
mass of rounded cells pushed up through the neurenteric canal (No. 19, p. 186). The 
phenomenon just detailed shows two important points, viz., the connection of the 
external blastoporic orifice with the region of Kupffer’s vesicle, if not with the actual 
structure itself, and the obliteration of the passage of connection, v.e., the neurenteric 
canal, by a plug probably pushed up from below. 
The section figured in Pl. IV. fig. 5d, and already referred to, passes through the 
precise region we have been dwelling upon, and a few loose cells alone obstruct the 
connection of the dorsal and ventral (enteric) groove, ne. The section is interesting as 
showing a portion of Kupffer’s vesicle, or the groove itself imbedded in a thick layer of 
periblast, per, as we have before described. 
Now the sections figured (Pl. IV. figs. 5b-5d, and fig. 6) clearly show the continuity 
* Fig. 8b is an intervening stage, when neither plug nor connecting bridge are visible. 
