coloration in the skin over them. There is also some coloration on the snout, 

 around the eyes, and on the cheeks, and there is a good deal of color on the back, 

 along the central line on both sides of the body, and around the vertebral column 

 inside of the body. The upper jaw is longer than the lower jaw, and there are 

 twenty to twenty-five teeth' in each. There are sixteen ossicles in the first dorsal 

 and thirteen in the second dorsal with a number of finlets. The anal fin has 

 fourteen and a number of finlets. The first dorsal is higher and darker in color 

 than the second dorsal. Its first three rays are almost equal in length, with the 

 more posterior ones gradually becoming lower. Points of difference between this 

 postlarval form and the adult are the broader body, larger head, eye, and mouth, 

 projecting snout, transparent wall of the cranial cavity, and the presence of an 

 air bladder. Another marked difference is the lack of development of the dark red 

 muscle tissue and its accompanying blood vessels along the sides of the fish. 



. Juvenile fish 60 - 75 mm long differ from the adults in their narrower breadth, 

 but otherwise they have the general form of the mature skipjack. Scales are al- 

 ready growing in their skin, the pyloric caeca are markedly developed and cover 

 almost the whole of the stomach, the blood vessels of the dark lateral muscle tissue 

 are developed, the dark muscle tissue is beginning to be differentiated from the 

 surrounding tissue, and ten or more teeth can be seen on the palatine bone. The 

 basibranchials are slender, the cerebellum is much smaller than the optic lobes, the 

 spleen is small, the gall bladder is long and slender, and the posterior and dorsal 

 surfaces of the body are covered with a uniform black color not due to chromatophores. 



Juveniles IOC mm or more in length show eight or nine transverse stripes of the 

 so-called carangid type or cybiid type (Figure 5). There are four such stripes on 

 the anterior half of the body and four or five on the posterior half. Those on the 

 anterior half are somewhat narrower and closer together than those on the posterior 

 half » The first stripe runs from the base of the first dorsal to the base of the 

 ventral, and the eighth stripe is anterior to the lateral projection or "keel" of 

 the tail. The ninth stripe is not clear but appears tc be at the keel. These 

 transverse stripes correspond to what are popularly called the "transverse rings" of 

 the tuna, but in some cases the stripes on the right and left sides of the body run 

 past each other instead of meeting. In the mature skipjack these stripes are some- 

 times seen on old large fish as they are hauled out of the water* The carangid-type 

 stripes fade out and become invisible on the belly, and at this time the keels be- 

 gin to develop. 



Of these larval and juvenile skipjack, the larval specimens of about 6 inn and 

 less in size were taken in plankton nets, while the postlarval and juvenile speci- 

 mens were all recovered from the stomachs of skipjack and other surface-dwelling 

 fishes. A boat from Makurazaki [31°16'N, 130°19'E] in Kagoshima Prefecture dis- 

 covered three juvenile skipjack 100-H0 mm in length among the bait sardines which 

 were being scooped up with a dlpnet as they swam alongside of the boat after being 

 scattered as chum on the fishing grounds. The fishermen very kindly brought them 

 back and presented them to me for research material. These are very interesting as 

 the first examples of juvenile skipjack taken alive, and a further point of interest 

 is the presence of the carangid type of markings on the two largest specimens. 



Genus Auxis 



A larval fish about U mm long which was taken in a plankton net off Takarajima 

 C29°9'N, 129°13'FQ June 8, 1924 (Figure 8) generally resembles the specimens thought 

 to be larval skipjack, however, there are few chromatophores in the cranial cavity 

 and the body cavity, there are four chromatophores on the posterio-ventral part of 

 the body, there are three spines on the surface of the preopercle, and the number of 



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