As to growth of Penaeus japonicus BATE, some contributions have been done by SENO (1910), KAJIYAMA (1933, '35), HIGURASHI (1937), and HUDINAGA (1942). Of them, the first and the third are dealing with the growth of the prawns cultured in a pond. The second deals with that of the animal of the Inland Sea of Japan. The last one is a work made on the growth of zoea- and mysis-stages of the creature by rearing with Skeletonema costatum. The growth rates known by SENO, HIGURASHI, and HUDINAGA are given in the Table 1. KAJIYAMA's conclusion is as follows: the larvae hatched out in late spring and early summer become about 3-6cm. in body-length without rostrum in early autumn. Those born in summer attain to length of 12.1 and 13.6cm. in male and female respectively in late June of the next year, and they go to spawning. It appears to be that the most of them measuring 15.1-18.2cm. in body-length in late fall close their life.
In the present investigation, to trace the growth of the prawn, an analysis of size-frequency distribution is made basing on a material monthly taken by a prawn-net from waters, ca. 7-15m. deep, off Hatazawa, Chiba Pref. (Tokyo Bay). The results yield by the present study seems to be well in agreement in all respects with that derived from the scrutiny carried out by KAJIYAMA. It may be added herewith that the size of adult differs apparently by sex: female is decidedly larger than male as seen in the Fig. 1, B.
