. <£tf^^^5 Text-fig. 44. External appearance of (a) Maurolicus muelleri; (b) Cyclothone pallida. Both, x 3. Reference to Text-fig. 43 will show that the brain of Maurolicus is large compared to that of Cyclothone microdon. (The standard lengths of the two fishes measured 35-0 and 36-5 mm. in the order just given.) This is even more true of the gill surface. On the lower part of the first gill arch of Maurolicus, the filaments have an average length of 1-5 mm. and there are 5 per mm. The number of lamellae per millimetre of filament is about 50. The first two corresponding figures for Cyclot
. <£tf^^^5 Text-fig. 44. External appearance of (a) Maurolicus muelleri; (b) Cyclothone pallida. Both, x 3. Reference to Text-fig. 43 will show that the brain of Maurolicus is large compared to that of Cyclothone microdon. (The standard lengths of the two fishes measured 35-0 and 36-5 mm. in the order just given.) This is even more true of the gill surface. On the lower part of the first gill arch of Maurolicus, the filaments have an average length of 1-5 mm. and there are 5 per mm. The number of lamellae per millimetre of filament is about 50. The first two corresponding figures for Cyclothone microdon are 0-2 mm. and 7 per mm. Once more there is ample evidence that the species from the upper mid-waters is the more highly organized and active fish. Apart from the greater development of the myotomes in Maurolicus, there is a striking difference in the nature and composition of the muscle, which may be seen in Text-fig. 43. The drawings are of cross-sections taken just in front of the caudal peduncle. Here the myotomes of Cyclothone microdon are formed of one type of large muscle fibre, each with a diameter of about o-i mm. Maurolicus has two types of muscle fibre. The inner parts of the myotomes consist of fibres with about half the diameter of those of Cyclothone, while those forming the outer parts are about half as small again. These latter are presumably red As the cross-sectional area of the inner parts alone is about equal to the corresponding area of myotomes in C. microdon, it will be seen how much finer in texture are the muscles of Maurolicus. Study of the density of the fibrils in the muscle fibres of these two species would be of interest. 1 Red muscle also forms a considerable part of the myotomes of the tunny-like fishes (Kishinouye, 1923), which are the most active of all teleosts.
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
