756 MR FRANK J. COLE 



Fig. 4. Lateral dissection of the left side of the tail of a 32 cm. Hag. x 3. Last two pre-eloacal 

 slime sacks removed. Dorsal and postero-ventral " fin rays " cut away. Obliquus and parietalis cut awav 

 ventrally — the latter behind the last slime sack only to expose the M. cordis caudalis. Myotomes and 

 post-cloacal slime sacks numbered from before backwards. 



Fig. 5. Dissection from the left side of a 36 cm. Hag, to illustrate the musculature of the body taken 

 at about the middle of the abdominal region. Perenyi fixation. x 2. A = anterior, D = dorsal. In 

 front, the M. obliquus and the slime sacks have been removed ; in the middle, the slime sacks only (leaving 

 depressions behind) ; whilst posteriorly the figure represents the surface of the body as seen after removal of the 

 skin. 



Plate III. 



Fig. 6. Broken series of transverse sections of the M. longitudinalis linguae and its tendon, selected 

 from the large series of a 25 cm. Hag, to illustrate the formation and fate of the tendon. Muscular tissue, red ; 

 tendinous portions, black ; soft pseudo-cartilage, dotted ; fibrous connective tissue, shaded. The figures 

 refer to the numbers of the sections; and for the lettering cp. the description of the tendon of the M. 

 longitudinalis linguae in the text. In 720, two small nerves are shown dorsally cut in transverse section ; and 

 in 625, a portion of the median ventral channel formed by the mucosa of the mouth appears dorsally. All 

 the sections were drawn with Edinger's projection apparatus to the same scale, and are x 26. 



Fig. 7. Transverse sections of muscle fibres, all taken from one 31 cm. Hag, fixed in formol + alcohol, 

 and all drawn to the same scale, in order to illustrate the differences in size. Stained with Mann's methyl- 

 blue-eosin. Zeiss apochr. 1*5 mm., apert. l - 30, conrpens. oc. 4. 



(a) Aplasmic fibre from the M. parietalis at about the middle of the back. 



(b) Plasmic fibre of ditto from the same region. 



(c) Medium-sized plasmic fibre from M. cordis caudalis. 



(d) Plasmic fibre from the dorsal division of the M. velo-quadratus. 



(e) Plasmic fibre from the M. velo-spinalis. 



(i) Contractile elements (sarcostyles or fibrils 1) ; (£) narrow elongated nuclei seen in transverse section 

 (generally central, and characteristic of the aplasmic fibres) ; (3) peripheral zone of sarcoplasm of 

 the plasmic fibres ; (4) peripheral round or oval nuclei of the plasmic fibres ; (5) peripheral blood 

 capillaries of the plasmic fibres. 



Plate IV. 



Fig. 8. Superficial muscles of the dorsal surface of the head of a 25 cm. Hag, as seen after removal of 

 the skin. Perenyi fixation. x 3. The anterior lobes of the brain are seen showing through the membran- 

 ous brain case in front of the second myotome. The small first myotome is not shown in the figure, being 

 covered, as well as the ventral portion of the second, by the dorsal extension of the M. obliquus. Note the 

 alternation of the myotomes of the two sides. The numbers indicate the identity of the tentacles and the 

 myotomes. 



Fig. 9. Superficial muscles of the left lateral surface of the head of a 30 cm. Hag, after removal of the 

 skin. Perenyi fixation. x 3. The dots indicate the line of insertion of the M. obliquus of the left side, 

 whilst the dashes mark the line of origin of the corresponding muscle of the right side, both of which have 

 been completely removed. The position of the first slime sack over the seventh myotome is shown by the 

 dotted outline. Tentacles and myotomes numbered from before backwards. 



Fig. 10. Superficial muscles of the ventral surface of the head of a 31 cm. Hag, after removal of the skin. 

 Perenyi fixation. x 3. The lateral portion of the M. obliquus is foreshortened by the perspective. The 

 fourth tentacle is displayed to illustrate its shape. Tentacles and myotomes numbered from before 

 backwards. 



Fig. 11. Same dissection and magnification as fig. 3 (q.v.), but with the following additional muscles 

 removed : — copulo-quadratus superficialis, copulo-quadratus profundus, copulo-glossus superficialis, lateral 

 head of the copulo-glossus profundus, copulo-palatinus, hyo-copulo-palatinus, and the palato-ethmoidalis 

 superficialis. Hard cartilage, red ; soft cartilage, blue ; hard pseudo-cartilage, blue dotted ; soft pseudo- 

 cartilage, obliquely striated. Tentacles numbered from before backwards. 



