380 
KAMAKIGHI KISH INOX’ YE : 
median septum. In Thunnus orientalis the two ureters meet in a figure like 
U, and in the other forms of the Japanese tunnies they meet like the figure 
Y. In Katswvonus the two ureters run quite near by in the posterior slender 
part of the kidneys, and finally unite to a median canal of some length. In 
Euthynnus and Auxis the two ureters are nearly separate. 
The urinary bladder is variable in size, form and position. Generally it 
is small and lies behind the peritoneum, but in Acantliocybium, Neofhunnus, and 
Auxis the bladder is large or much elongated and is found in the abdominal 
cavity, suspended in the mesentery or between the two genital glands and above 
the rectum. 
REPRODUCTIVE SYSTEM. 
In the scombroid fishes the generative organs are paired, large, and elon¬ 
gated sacs on the roof of the abdominal cavity, suspended in a fold of the 
peritoneum, and extend along almost the whole length of the cavity. The organs 
on both sides are symmetrical, nearly equal to each other in form and size. In 
Auxis the generative organs, both male and female, extend backwards along 
the side of the anal fin. This backward extension is not so marked as in the 
case of the female flatfish, but it3 cause is the same—the narrowness of the 
abdominal cavity. In scombroid fishes the genital glands generally seem to 
ripen in the third year of growth, that is when the fish is two years old. 
The testes have trenchant edges, hence more or less lanceolate in cross- 
section, and when ripe, milky white to light yellowish in colour. The ovaries 
are fusiform, more or less roundish in cross-section, and yellowish in colour, and 
greater in volume than the testis. In tunnies the gonads grow very large, 
attaining several kg. in weight. As the eggs in them are minute as in other 
fishes, their number is no doubt enormously large. 
Scombroid fishes generally spawn in the warm season, and in the open 
sea. So far as I know, Scomber japonicus, Cybiurn niphonium, and C. koreanum 
are the only species which spawn in our bays and inland seas. Spawned eggs 
and larvae of the plecostean fishes are still unknown. 
The generative organs of both sides coalesce near the hind end, and the 
lumen in them imite to a short and wide duct, which opens as a transverse 
slit on a papilla, behind the anus. 
