A comparison in developmental process of larval digestive system was made in 18 species of teleosts. Based on the morphological features of digestive system, teleost larvae may be roughly divided into two main groups. In newly hatched larvae belonging to the first group, digestive organ is scarcely formulated; in those of the second group, digestive organs have differentiated in a certain extent at this stage, for example, mouth opened, liver and pancreas differentiated, and so on. The former is observed commonly in the larvae derived from pelagic eggs, and the latter represented by those came out from demersal eggs. But there is a considerable variation in the degree of differentiation of the system at the time of hatching among the larvae from demersal eggs, and these characteristics are believed to have developed closely connected to the spawning habit of the species as well as to the behaviour of the newly hatched larvae. No marked specific difference is found as to the sequence of formation of the organs, and the system has developed to a certain level at the end of prelarval stage. Most of the larvae show the process of development as follows; differentiation of gill opening-liver-mouth; anus-pancreas; gall bladder-gill arch-oesophagus; stomach; intestine-sphinctor of posterior intestine-pancreatic duct; bile duct. Some prelarvae hatched out from demersal eggs have oral teeth, pharyngeal teeth, taste buds and goblet cells, but lacked the gastric gland and pyloric caeca. Trout and probably salmon are exceptional. It is generalized that the digestive system in prelarval stage may be regarded as the most simplified among these of adult fish.

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Tne development and morphology of lateral scutes in Japanese sticklebacks has been studied for more than 15 years by the author. The present paper is one of those serial works, and deals with the species, Pungitius kaibarae (Tanaka) or in Japanese “minami-tomiyo”. The total of 30 specimens, ranging 18 to 51 mm in total length and collected at Nishioji, Kyoto City in June 1958, were studied. This species is now about to extinguish in this area. In P. kaibarae the scutes develop firstly in the juvenile, no more than 18 mm in total length, instead of 20 and 15 mm as observed in P. sinensis and P. pungitius, respectively. In P. kaibarae the first scutes appear on the caudal peduncle followed by those on the dorsolateral part of body above pectoral fin, and then each group grow forward and backward respectively, eventually formulating the Trachuran series of scutes; such pattern of scute formation, though observed in the species of Gasterosteus, is not traced in the species of Pungitius except in P. kaibarae. The feathershaped scutes in P. kaibarae are more blunt than in P. sinensis, and the central ridge on the rhomboid scutes in the former species develops in later stage than in the latter. The scutes in P. kaibarae, like in P. sinensis, P. pungitius and P. sp.(“musashi-tomiyo”, Japanese name), were ranged in a single series; the scutes in the present species seldom overlapped one another, sometimes, completely iso-lated anteriorly. Those findings favor to recognize P. kaibarae as a distinct species, which some authors have treated as a subspecies of P. sinensis or P. pungitius.

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The Oikawa, Zacco platypus, is the popular game fish which widely inhabits the rivers and ponds all through Japan except Hokkaido. Along with the study on the life-history, ecology and population of the species, which has been carried out since 1965 mainly in the water of the River Aki (a tributary of the River Tama flowing into Tokyo Bay), the authors have studied the relationships between the maturity and sexual characters in the anal fin. Based on the inspection of 1628 specimens collected monthly by a cast-net from November 1965 to September 1966 and in May 1967, and by angling in August 1966, the following results were obtained. 1) The males during the spawning season (June to August) were characterized by well-developed pearl organs, red and bluish green color on the side and enormously grown anal fin. These mature males, dominated by age group III⁺ and a half of males of age group II⁺, exhibited breeding reactions and died out no later than September after spawning. 2) On the other hand, another half of males of age group II⁺ continued to grow in summer and became matured at III⁺ year old in the following summer. These II⁺ males were termed “non-mature” males against the above mentioned mature males. These males showed no secondary sexual characteristics and having only thin thread-like testis through out the spawning season. 3) The morphological change of anal fin was observed also in mature females, but to a lesser extent as compared with mature males. Mature females began to spawn at II⁺ years and died out after the second spawning at III+ years. 4) It is evident that Zacco platypus more than 80 mm in total length can be sexed during spawning season and the degree of the sexual maturation, particularly in the males, may be quantitatively measured by the length of anal fin. 5) The cause of the condition that males of age group II+ are mature or “non-mature” in spawning season was suggested through reading the history on the scales examined. The appearance of “non-mature” males in age group II⁺ was discussed in relation to the population density.

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The four species of sea-bream referred to the genus Chrysophrys in the Indo-Pacific area have been treated in the state of a confusion as to their generic and specific characters. In the present study dealing with the three species, C. unicolor from West Australia, C. auratus from New Zealand and C. major from Japan totalling 137 specimens, it was clarified that the three species are distinct from each other: They are distinguished by the length of head and the distance from the tip of snout to the origin of the first dorsal. The skull of these species also showed a clear specific difference especially in the following features: the growth stages when the frontals fuse; the portion and shape of the thickening of the supraoccipital.

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[in Japanese]

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