抄録
The spiny dog fish, Squalus suckleyi, are captured in abundance by trawl nets in the south-western part of Sea of Japan in spring (March to April).
The writers examined on the frequency distribution of total body length, the development of genital gland and clasper with growth as well as the states of pregnancy and parturition in the same district and obtained the following results:-
(1) The modal value of the total body length of the spiny dog fish in spring is 110-120cm in female and 80-90cm in male.
(2) The male seems to mature sexually at the total body length of 70-80cm.
(3) The female becomes pregnant for the first time at the total body length of 90-95cm.
(4) Some ova which are to be born in the following season begin to develope in ovary in connection with the development of embryo in uterus. There seems to exist a certain relation between the decreasing of diameter of yolk sac and the increasing of that of ovum in connection with the development of the embryo in uterus. Those ova are thought to enter the uterus shortly after the embryos are delivered. So the female seems to be always pregnant after she has matured sexually for the first time.
(5) The spiny dog fish are thought to have a delivering season at least in spring in the south western part of Sea of Japan.
