aon MR. E. W. SHANN ON THE 
tend to indicate that the division line is horizontal rather than 
tangential; that is to say, they support Schneider’s view. 
Chevrel’s diagram of the pyramidical disposition of a caudal 
myomere has been reproduced on p. 322 (text-fig. 1); the 
accompanying illustration (text-fig. 2) will serve to convey a more 
realistic view of the manner in which the pyramids fit one into 
the other. Let us follow in turn the course of six myomeres 
represented in the text-figure. 
First myomere. —This is seen at the surface on the right of the 
text-figure(1). In the mesio-dorsal portion (J/.D.) its fibres are 
directed from above anteriorly to below posteriorly, in the 
latero-dorsal portion (Z.D.) the fibres are directed from below 
anteriorly to above posteriorly ; in the ventral moiety (Z.V. and 
M.V.) this sequence is repeated. The dorsal moiety is separated 
from the ventral by the lateral line (J./.) and by the “red fibres ” 
on either side of it. Looking into the section, we find the first 
myomere (1) in the form of an acute angled triangle with 
its base abutting on the vertical septum, in which run dorsally 
the neural spines and ventrally the hemal spines; it presents a 
similar appearance both in the dorsal and ventral moieties. 
Second myomere.—Seen at the surface immediately behind the 
foregoing, it takes a similar course; the posteriorly directed 
apices of its V-shaped bends are broken, however, by the section. 
Following its course into the section we find that it presents a 
V-shaped mass which bestrides the triangular section of the first 
myomere. 
Third, fourth, and fifth myomeres.—These are seen externally, 
each at four points, as a series of gradually vanishing segments 
of the V-shaped arms (the fifth myomere, however, does not 
appear superficially in the central region). In section each 
presents four quadrangular faces, two above and two below the 
horizontal septum. Near the middle line the faces become 
curved, so that they present a convex surface to the exterior 
and a concave surface to the interior. 
Siath myomere.—This does not appear superficially, but is seen 
as a roughly triangular mass on either side of the horizontal 
septum. The base of the dorsal triangular mass rests against 
the body of the vertebra, that of the ventral one against the 
hemal arch. The outer angles of these triangles, unlike those of 
the sections of the first myomere, are rounded off, and fit into the 
concave inner surfaces of the fifth myomere. 
Having obtained a sequence of views of a series of consecutive 
myomeres, let us proceed to reconstruct from them the conform- 
ation of a single mvomere. As the ventral moiety of a myomere 
is the counterpart of the dorsal, it will be sufficient to confine 
our remarks to the latter. 
It is evident from the foregoing observations that a myomere 
is not visible superficially in its most anterior region, We have 
seen it (6) as a triangular area in the angle between the centrum 
and the horizontal septum. By dissection it is easy to demonstrate 
