78 M. SASAKI, 
Prussian-blue or tinged a little with purjjle, and tlie luminosity is strong 
enough to absorb the light of other luminous organs. Wlien the living 
animal was placed on a glass plate, which was put directly on the case 
of the dry plate of the photographic camera, and then exposed for 4 
seconds with the Lion's dry plate of the special rapid no. 230, the light 
of this brachial organ was distinctly taken on the dry plate, although 
those of other organs made no impression. 
Minute Organs Scatiercd on the Ventral Surface of tlic Whole Body. There 
are numerous minute organs distributed on the ventral surface of the 
mantle, head and siphon, and they are also on the third and fourth arms. 
The external appearance as well as the histological character is the same 
but with some diversity in size. 
The organs on the mantle differ in number between male and female, 
i. e. 566-687 in the female and 450-543 in the male as counted in 10 
specimens of each sex. They are entirely found on the ventral half of 
the mantle, and the arrangement is not quite regular, but more or less in 
series showing slight bilateral symmetry. The distances between the 
organs are nearly equal but with slight gradual increase towards the 
lateral sides as well as towards the posterior end of the mantle. 
The organs on the siphon are about 47 in number, alike in male and 
female, and the arrangement resembles those of the mantle. 
The organs on the head are about 180, alike in male and female, 
arranged somewhat in several series with the anterior organs of these 
series connecting with the series of the same organs on the arms. Besides, 
along the margin of each eye-lid there is another series, which consists 
of larger and smaller organs arranged alternately. 
The organs on the fourth arms are arranged in 3 series, the middle 
one of which is the longest, consisting of about 28 organs, and connec- 
ting distally with the brachial organs, beyond which yet 3 other small 
organs are found. The brachial organ from the point of view of situation 
appears to have evolved from the minute organ but of course with great 
