The juvenile specimen which is slightly less than 6 ram long,, excluding the 

 caudal fin, has a very large head, occupying about one-half of the total length. 

 The eyes and the mouth are also large and the snout is sharply pointed „ Ju3t as in 

 the juveniles described above, the upper jaw is slightly longer than the lower. 

 The posterior edge of the articular bones projects ventrally, and the greatest 

 breadth of the body is at this projection. From this point anteriorly it becomes 

 rapidly narrower and sharper, while posteriorly it tapers more gradually. There is 

 a single nasal pore, and both the upper and lower jaws have thirteen or fourteen 

 teeth on each side,. There are four teeth on the palatine and five on the lower 

 pharyngeal bone. The preopercle has -three spines on its ventral edge, one at the 

 angle, and three on the posterior edge, of which the one at the angle is the longest. 

 There are also two small spines on the surface, and one rather large spine on the 

 surface at the posterior part of the head. The pectoral fins are comparatively 

 large with their posterior ends reaching almost to the origin of the> anal. The 

 dorsal is low and not yet differentiated into the first and second dorsals and the 

 finlets, nor is the anterior part o? it particularly high. The first spine of the 

 dorsal is somewhat posterior to the anterior edge of the fin membrane and is a lit- 

 tle shorter than the second spine. The spines and ray 3 are not yet completely de- 

 veloped,, The ventral fins are located between the opercles, and are triangular in 

 shape and pointed posteriorly. The caudal fin is forked. There are melanophores on 

 the walls of the cranial cavity and the body cavity and on the cheeks. Some black 

 coloration is also visible on the upper and lower ends of the snout, but it does not 

 form star- shaped chroma to phores. Just as in the larval specimen described above, 

 there is one large chroma to phore on the ventral side of the caudal peduncle. The 

 fins are all still colorless., Posterior to the intestine, which is covered with 

 melanophores, there car. be seen a large urinary bladder which opens posterior to tba 

 anus. The anus opens at a point slightly posterior to the center of the body exclud- 

 ing the caudal fin. 



Among the specimens which I have studied, the smallest which I have definit3ly 

 identified as a skipjack hr.s a total length of 26 mm. It was taken from the stomach 

 of a skipjack at Gonsone [29°47*N F 129°25'F3 by Mr. Gisuke Umemoto on April H, 1924- 

 and was reported on page 92 of Volume 4, Number 2 of this journal as possibly a 

 larval innsawara [Cybium chlnense Schlegel] (Figure A), It was thought at first to 

 be probably a cybild because of a mistake made in counting the precaudal vertebrae, 

 but by completely removing the muscles from one side and examining the bones of the 

 head and the internal organs it was ascertained that the specimen is a skipjack. In 

 this specimen the breadth of the body has greatly increased so that it is roughly 

 equal to the breadth of the head, and at the same time the body has also become much 

 longer. The anus has moved posteriorly and opens just anterior to the anal fin. The 

 fins are on the center line of the body, and the unpaired ones are all differentiated 

 and have assumed forms resembling those of the adult fish. The opercular spines 

 have degenerated and are no longer conspicuous. The stomach has become a large 

 pointed sac running almost the whole length of the body cavity and pyloric caeca 

 have developed on both the anterior and posterior sides of the duodenum. Further- 

 more, the presence of inferior foramina in the precaudal vertebrae leaves no doubt 

 that this is a postlarval skipjack. It can be seen from the surface that the post- 

 clavicle has developed diagonally from below the pectoral fin, and many melanophores 

 have developed on the walls of the body cavity so that it looks faintly blackish 

 viewed from the outside. The spleen is small and is located to the right of the 

 duodenum. On the top of the head between the eyes there are two pairs of black spots) 

 an anterior and a posterior pair, with their edges touching. These spots are where 

 the melanophores in the walls of the cranial cavity show through the flesh. The 

 anterior pair surround the olfactory lobes, and the posterior pair are around the 

 optic lobes. They are more developed than in the earlier specimens, but they become 

 invisible later due to the growth of the muscle tissue and the development of 



