FREEDINSTEPURE OF SCIENCE 
ON THE LIFE HISTORY OF AN ECONOMIC CUTTLEFISH OF JAPAN 
Number of 
Number of — specimens Number of Length of 
Date of specimens sexually mated nidamental Length of 
No. catch examined matured specimens gland mantle 
i Sept. 7, 1918 3 B 3 65- 90 mm. 220-250 mm. 
ii Octin2750 se 5 5 5 7o- 95‘ 210-248 “ 
iti IDyeeyy ayy I fe) I OMe 2I52 naace 
iv Jan. 24, 1919 2 I 2 Ee 9a) 2ACH es 
Vv Rebaians sue 4 fe) 4 gi joy Ue 230-235 “< 
vi April 12, ‘ 5 I fo) es 198-232 “ 
Vii uliysetossen 3 I I o-115 “ 17 82312 
Vili JaNieeay GE 6 4 4 o-105 “ I1s—255 “ 
ix SepearOnme: 7 4 7 75-100 “ 257-285 “ 
x Septa2 7a 9 6 9 79-121 “ 230-279 “ 
xi Ofez, avi, © 9 8 9 gi-121 ‘“ 255-288 “ 
xii Dec. 26, ‘“‘ 9 I 8 C= FO TO 3O3) en 
xili Jan. 5, 1920 3 I 3 60-106 “ 260-303 “* 
MATURE EGGS AND THEIR INCUBATION IN THE NATURAL 
STATE 
The mature eggs in the ovary or oviducts are easily distinguished from 
immature ones; the former are brown and transparent, while the latter are 
white and opaque. ‘They are oval, measuring 0.6 mm. byo.7mm. The eggs 
deposited in the natura] state have not yet been seen by naturalists nor known 
to any fishermen with whom I am acquainted. No exact datum on this point 
has been secured from the plankton investigations hitherto described, even 
though it has been suggested by observers that Oegopsid Cephalopods in 
general discharge eggs floating on theocean. My efforts to prove them in the 
plankton collections made in Oki have also been in vain, although these collec- 
tions represent every month in a region where mature females occur nearly all 
the year round. At first sight this seems very strange, bearing in mind that 
the species is among the commonest inhabitants in Japanese waters. To get 
light on this difficulty we have to turn to the anatomical details in relation to 
the nidamental glands and genital openings. 
The nidamental glands are fused together and situated at the midventral 
part of the viscera. When mature they become so large as almost to cover the 
ventral surface of the visceral mass, and external orifices of the glands are found 
widely separated from those of the oviducts, in contrast, for instance, to 
W atasenia which is known as depositing pelagic eggs. Moreover, the latter 
genus has no seminal receptacles on the buccal membrane. ‘The peculiar 
topographic relation of the genital openings to the nidamental orifices as seen 
