686 MR FRANK J. COLE 



been drawn from one of the medium-sized fibres, the largest being about the size of the 

 red fibre figured from the parietalis. The sarcostyles (1) are generally quite small and 

 closely packed, but may be of variable size. There is no appreciable internal sarco- 

 plasm, and I have only very rarely seen internal nuclei. Most of the fibres have 

 uniformly small sarcostyles, and the transverse striation is somewhat indistinct. The 

 peripheral sarcoplasm (3) is relatively more abundant than in the parietalis red fibre, and 

 contains strings of large oval or round nuclei (4). Although the muscle is very vascular 

 (5), the capillaries are not arranged in a definite rich plexus round each fibre as in the 

 parietalis red fibre — perhaps not necessary, owing to their smaller size. 



M. velo-quadratus. (Fig. 7, d.) 



Also consists of red fibres only. They are of practically uniform size, much smaller 

 than the red fibres of the parietalis, and about equal to the medium fibres of the cordis 

 caudalis. The sarcostyles [1) are exceedingly small, of uniform size, and fairly closely 

 packed, and there is no appreciable internal sarcoplasm. The transverse striation 

 generally is faint, and there is an extensive peripheral zone of sarcoplasm (3) with large 

 unusually round nuclei (4-). I have seen a large nucleus in the centre of the sarcostyles, 

 but it may be said that the nuclei are typically peripheral. The muscle is very vascular 

 (5), more so than the cordis caudalis, but not to such an extent as the red fibres of the 

 parietalis. There is no plexus round each fibre as in the latter muscle, but large 

 capillaries penetrate very freely between the fibres. 



M. velo-spinalis. (Fig. 7, e.) 



The histology of this muscle agrees with that of the velo-quadratus, but the follow- 

 ing points may be noted. The fibres are smaller, and there is occasionally a patch of 

 sarcoplasm in the centre of the fibre in which I have (rarely) found a central nucleus, 

 but neither of these features is at all characteristic of the muscle. The striation is 

 very faint and the muscle is highly vascular (5). 



3. M. tentacularis posterior. (Figs. 8, 9, 10, t.p.) 



J. Muller, ZururJizieher der Tentakeln (p. 258). 

 Arises just behind and over the eye in the apex of the angle formed by the two 

 limbs of the second myotome, or in some cases by the upper limb of the second myo- 

 tome and the backward extension of the first (cp. fig. 9). The origin is from the 

 strong membrane constituting the fascia superficialis externa of J. Muller. The M. 

 nasalis arises largely from the same membrane. The eye lies between this muscle and 

 the palatine bar. The muscle passes forwards, most of it at the side of the lateral 

 wall of the brain case. Opposite the posterior end of the nasal capsule it begins to 



