‘6 TRANSACTIONS OF WAGNER 
ON THE LIFE HISTORY OF AN ECONOMIC CUTTLEFISH OF JAPAN 
agencies which regulate and have extraordinary influence upon ecologic life 
of the animal, consisting in its distribution, migration, and habit of repro- 
duction. It has been considered above, that the seasons, warmer and colder 
waters, affect the catch; a weak daylight seems also to favor the creature, but 
the chief natural agency favoring it is a certain temperature that stands 
between 10° C. and 17°C.., as it flourishes best in this temperature of water. As : 
thermal regulators of ma- 
rine water are first of all 
to be taken into account 
the oceanic currents. Let 
us take a glance at the 
currents around the Japa- 
nese Islands. 
As is very well known, 
we have on the Pacific 
side two principal cur- 
rents of different tem- 
peratures (fig. 6). The 
warmer is the well-known 
Kuro-shiwo (the Japan 
Stream) which is peculiar 
by its high salinity and 
flows northwards and 
eastwards along the Loo- 
choo group and the south- 
Fic. 6. ern coasts of Kiushiu and 
Currents in the upper water-layers of the seas around Japan. Shikoku, extending a lit- 
The smaller arrows are referred to Wada’s observations of the 
drift bottles, and the larger arrows, to the current chart for ] re northerly than 
the North Pacific, Jan.-Dec., published by the Hydrographic Be re y 
Department, Tokyo. 
the middle part of Hon- 
shiu. Hereafter, it di- 
verges from Japan so as to form the North Pacific Drift. The colder current 
is known as Oya-shiwo, which flows west and south along the east coast of the 
Kurile Group and of Hokkaidé, and reaches the northern part of Honshiu, 
where it meets with the aforesaid Kuro-shiwo. Both currents vary in strength 
in different seasons: the Kuro-shiwo is strongest in the warmer season and 
weakest in the colder, while the reverse is true of the Oya-shiwo; hence the 
