96 BULLETIN OF THE BUREAU OF FISHERIES. 



FemaU salmon (no. Iiy), length g40 mm., weight 8,24^ grams, taken from the Whilcomh trap located in the 



bend of Bakers Bay. 



This salmon was more slender than no. iii, was a clean fish, but did not appear in as prime condition. 

 The ovaries weighed 510 grams. The flesh appeared less oily and was very pale in color, especially in 

 the caudal peduncle. 



Microscopic examination of the trunk pink muscle (trans-verse section, Kji). — This section is taken 

 ventral to the lateral-line septum. There is very little intermuscular fat. Even along the myocommata 

 there are only a few droplets and these are of small size, from i to 10 /j in diameter. The very largest 

 drop seen was only 15 /i in diameter. 



The substance of the muscle fiber contains a supply of liposomes arranged in chains throughout 

 the mass of the fiber. These liposomes run from 0.3 to 0.5 ;i in diameter. The section is cut obliquely, 

 making it difficult to interpret the point, yet it is obvious that the liposomes are in greater numbers 

 along the superficial region of the fibers while the deeper portion of the fibers is relatively poor in lipo- 

 somes. This gives the section as a whole a mosaic-like appearance. The point is not absolutely certain, 

 yet I am convinced that tliis increased quantity of liposomic fat is under the sarcolemma and between 

 the more superficial layer of fibrils. 



A section taken from the dorsal division of the deep lateral muscle has a less amount of fat than that 

 from the ventral. The fibers of this section are very compactly arranged and the outlines are corre- 

 spondingly sharp and angular, similar to that shown in later stages. (See salmon nos. 125 and 126.) The 

 diameters of the fibers themselves vary between 30 and 150 «, rather smaller than the average pink 

 muscle fibers. 



There is a verj' small quantity of ver)' fine liposomes within the substance of the fibers. In many 

 fibers no liposomes are to be distinguished. In the smallest fibers shown in the field, those 30 /i in 

 diameter, the liposomes are present in the middle of the fiber. la the mediu.m-sized fibers the lipo- 

 somes are largely around the superficial area of the fiber and are from 0.2 to 0.3 fi in diameter, rarely 

 larger (1/12 oil immersion). In the middle of these medium-sized fibers and in most of the body of the 

 large fibers, liposomes are much fewer and exceedingly small, scarcely discernible. 



The smallest fibers often have rings of ve.-y small fat droplets, the droplets running from 2 to 3 /i 

 in diameter. These droplets are just under the sarcolemma. In areas where they are more numer- 

 ous there are occasional fat drops 15 ;( in diameter located between the muscle fibers. 



Microscopic examination of the caudal pink muscle (transverse sections, KlQ and 20). — These sections 

 of caudal muscle show a markedly less amount of fat than from the dark muscle. The type of arrange- 

 ment is that of the trunk muscle except that there is less intermuscular fat. 



The intramuscular fat is also conspicuously less in quantity. The liposomes are practically absent 

 from the larger fibers and are very minute and few in numbers in the smaller fibers. 



Microscopic examination of the trunk dark muscle (transverse section, Ky). — The fat droplets are rela- 

 tively small in this preparation, notably smaller than in salmon no. 115. The intracellular fat is evenly 

 scattered through the substance of the dark fibers. The liposomes vary from 2 to 5 /i in diameter (tissue 

 cut fresh). In the regions which have the smallest amount of fat the number of droplets of the larger 

 size which are so prominent in fish no. in are greatly reduced in size, running from i to 5 /i in diam- 

 eter. In certain areas of the section lying near the connective tissue partitions there are small groups 

 of dark fibers which apparently have their fat reduced greatly below the average. Such fibers will 

 contain irregularly placed liposomes from i /(down to a just visible size, 0.2 to 0.3, /i, while adjacent 

 fibers will have a more prominent loading of fat in which the droplets average from 3 to 5 ^ in diameter. 

 Also the number of droplets in the latter fibers is greater than in the former. This picture suggests 

 the thought that the fat of the dark muscle is being removed along the course of the larger blood vessels. 



Microscopic examination of the caudal dark muscle. — Insufficient study was made of the caudal dark 

 muscle, but the rather poor sections bring out one point, namely, .that the fat is reduced much below 

 the average and that the fat droplets are massed around the surface of the fiber. 



Male salmon (no. llS), length 040 mm., weight 12,4^0 grams, taken in McGowan & Co.'s trap at the 

 mouth of Bakers Bay near the Fort Canhy Dock. 



This fish was a deep smooth specimen, skin bright and clean, no sea lice, head shaped like the 

 female, medium depth, a splendid specimen apparently comparable to no. iii. The testes were quite 

 small and immature. 



