LATERAL MUSCLE IN TELEOSTEI. 323 
change of a single half myomere, dorsal or ventral, from a single 
bend to a double bend *. 
Chevrel (1) has given a lucid description of the conical, or 
pyramidical, structure of the myomeres forming the lateral 
muscle. His diagram illustrative of the apparent and the real 
structure of a single typical Teleostean myomere is reproduced 
here (text-fig. 1). “At Bis seen the dorsal posterior pyramid, at H 
the anterior dorsal pyramid, at H' and D the ventral pyramids, 
while C indicates the lateral line. It is only necessary to add that 
in the abdominal region the dorsal moiety (portion épiaxiale) alone 
exhibits this double evagination ; the ventral (portion hypoaxiale) 
is ribbon-like. Chevrel recognises a horizontal septum dividing 
completely a dorsal from a ventral moiety; but there isno mention 
of stratification in any area of the lateral muscle. The carinales 
(m. gréles) are the homologues behind the pelvis of the rectus 
which is found in the thoracic region. 
Tue AUTHOR'S OBSERVATIONS. 
Having now stated the principal views extant as to the 
divisions of the lateral muscle in Teleostei, the conflicting nature 
of these becomes patent. I shall next proceed to formulate a 
classification of the parts of the lateral muscle, retaining such 
features as are agreed upon by the majority of the investigators 
whose work I have studied, and discarding those which I find to 
be incapable of general application. In this classification no new 
terms will be introduced, preference being accorded to those which 
are deemed most descriptive. I wish it clearly to be understood 
that I regard any such classification, in the light of our present 
limited knowledge, as essentially empirical anne tentative. 
That the so-called lateral muscle of fishes is, more strictly 
speaking, a sequence of serially homologous transverse muscles 
(myomeres) is the fundamental starting point upon which all 
investigators are agreed. Setting this fact in the background, 
but never letting it completely out of sight, let us proceed first 
to map out the superficial divisions of this muscle in a Teleostean, 
and then to prove by dissection the morphological value of these 
divisions. 
No specified type has been taken; but the description, and 
herein lies what merit it possesses, is so generalised as to apply 
to the majority of Teleostean fishes. Exceptional cases will be 
cited wherever practicable. 
(1) Haternal Conformation. 
The most obvious longitudinal division giving rise to a dorsal 
and a ventral moiety is formed by the passage of the lateral line. 
Upon this point there is but one voice. 
* This process can be very clearly followed in Knauer’s drawings of Salmon 
sections, op. cit. pl. 11. figs. 15-19. 
Proc. Zoou. Soc.—1914, No. XXIT. 22 
