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quasi-lingual musculature, as explained in Part I) consists of 18 seg- 
ments, the first (Z) being situated immediately behind the buccal 
funnel and the last (JZ) between the last two gill-clefts. These ventro- 
lateral myotomes are continuous anteriorly across the mid-ventral line 
with those of the other side by means of a thin membrane which 
covers over the copulo-glossus rectus, hyoglossus and hyo-hyoideus 
muscles. The membrane is represented in figure 19 by oblique lines, 
The groove containing the gill-openings, which extends’ from the 
region of the eye to the last gill-cleft, forms of course the line of 
separation of the ventral portions of the anterior seventeen dorsal 
myotomes from the dorsal portions of the eighteen segments of the 
sub-branchial myotome musculature. In front of the eye there emerge 
four large nerves to be described later. The definitive basilaris muscle 
(VIL) and its derivatives, the spinoso-semianularis anterior (VIII), 
the spinoso-semianularis posterior (IX) and the “latero-semianu- 
laris” (X) had also better be described at a later stage of dissection. 
Portions of the copulo-glossus rectus (XJ), hyoglossus (XII), hyo- 
hyoideus posterior (XIII), hyo-hyoideus anterior (XIV) and hyo- 
branchialis (XV) muscles and the anterior dorsal (A.D.) and posterior 
dorsal (P.D.) cartilages and the ligaments respectively uniting the 
lateral process of the median ventral (C.A.L.) and the anulo-glossus 
muscle (XVJ) with the anular cartilage are also shown in the drawing. 
Figure 19 shows some of the above-named structures in ventral 
aspect. 
In figure 20 the dorsal myotomes have been for the most part 
and the sub-branchial myotomes completely removed, the middle portion 
of the anulo-glossus (XVI) has been cut out and the anularis 
musculature (VI) cut into. The anularis (VI) consists of three 
layers—a. externus, a. medius and a. internus—the middle layer being 
two or three times thicker than outer and inner layers. The function 
of these three layers is of course the active contraction of the buccal 
funnel in the act of fixation and the passive support of its walls when 
fixed (its cavity forming a partial vacuum) against the external pressure 
of the surrounding medium. The spinoso - semianularis anterior (VIII) 
is a thin elongated strip of muscle, lying dorsal to and in contact 
with the anularis, which is attached anteriorly to the upper surface 
of the anterior corner of the anterior dorsal cartilage and posteriorly 
to the upper outer border of the styliform for the greater part of its 
length. The fibres of this muscle are disposed more or less parallel 
