SEA-FISHERTIES LABORATORY. 357 
innervates each tentacle, passing up the centre and giving 
off branches to the sense cells. 
If the mantle lobe of one side, preferably the right 
(where the adductor muscle is attached much nearer to 
the hinge line), be removed, the general topography of 
the viscera can be easily made out. ‘The various organs 
thus exposed are shown in PI. II, fig. 1. The single 
adductor muscle occupies a fairly central position 
(fig. 1, A.w., A.s.), and serves as the support for the 
greater part of the animal which surrounds it. Against 
the hinge line is the deeply pigmented, green-black 
looking gland, the so-called liver, which will be referred 
to as the digestive gland (fig. 1, Yg.). The gills (Br. a., 
Br. d.) are very conspicuous structures, lying between the 
visceral mass and the mantle and attached to the latter 
on the right side, so that if the mantle were cut away 
close to the adductor the gills on this side would also be 
removed. They consist of a long series of orange coloured 
filaments suspended from a basal lamina. 
The body proper may be divided into :—(1) Viscero- 
pedal mass, (2) the pericardium and rectum, and (3) the 
renal organs. | 
The viscero-pedal mass consists of (a) the Digestive 
Gland which is situated at the posterior and dorsal 
extremity and encloses the stomach, and (bd) a long, 
flattened, tongue-shaped reproductive portion, of a brown 
colour over the whole area, or if the gonads are ripe— 
white for part of its length (the testis), and pink or 
brillant scarlet for the rest (the ovary). There is no 
distinct division between the digestive gland and this 
latter portion of the viscera, but just where they are 
contiguous the rudimentary foot (fig. 1, /’.) is situated. 
It is roughly cylindrical in shape; the distal portion, how- 
ever is sucker-like, with a deep cavity. The foot, it will 
