ANATOMY OF LOLIGO. 257 
short muscular canal with a large orifice extending on 
the ventral side to the base of the tentacles. Through 
this siphon passes excrementitious matter as well as the ink, 
and the stream of water which is forcibly ejected from the 
siphon, thus propelling the squid through and sometimes 
out of the water. 
The two gills (Fig. 208, g), are large, long slender bodies, at- 
tached by a thin membrane to the inner wall of the mantle, 
and are quite free from the visceral mass. From the bran- 
chial vein arise two rows of lamella like the teeth of a comb. 
At the base of each gill is a flatted oval body, the “ bran- 
chial heart,” or auricle (Fig. 208, 52). The auricles are quite 
separate from the large four-cornered flat ventricle (Fig. 
208, %), lying in front of the stomach, and which throws off an 
artery from each corner, the aorta being the largest, and 
passing parallel to the cesophagus, while a large vein (vena 
cava) is sent off to the gills from a circular sinus in the 
head. 
The nervous system is more complicated than usual in 
Mollusca, and is very difficult to dissect. In Loligo Pealti the 
highly concentrated nervous system is mainly contained in an 
imperfect cartilaginous brain-box (cg), a slight anticipation of 
the skull of the Vertebrates. The brain (supracesophageal 
ganglion, Fig. 208, d) rests upon the very large optic nerves, 
which dilate at the base of the eye, the latter being partially 
imbedded in sockets in the brain-box. The visceral (parie- 
tosplanchnic) ganglion lies beneath and a little behind the 
brain, supplying the nerves for the ears (otocysts), which 
are enclosed in the cartilaginous brain-box, and there is a fine 
canal leading from the ears to the surface of the body, so 
that, as Gegenbaur states, it is possible to distinguish a mem- 
branous and a cartilaginous labyrinth, analogous to the 
similar parts found in the Vertebrates. The pedal ganglion 
(Fig. 208, ) is paired with the visceral ganglion (Fig. 208, »), 
but lies in front of it, behind and under the bulbous pha- 
rynx, and from it arise ten nerves (#), which are distributed one 
to each arm, passing between the two rows of suckers. Two 
smaller ganglia, the superior buccal and inferior buccal, lie 
one above and one below the beginning of the cesophagus. 
