LYMNEIDZ OF NORTIL AMERICA. 15 
leaves the right visceral ganglion near the right pallial nerve, and 
shortly joins a similar one from the abdominal ganglion, the combined 
nerve passing to the vagina, the anterior part of the mantle and the 
respiratory cavity. The left ganglion sends off a single long nerve 
which innervates the mantle along its sides (20). 
The ABDOMINAL GANGLION (4), which is really two ganglia fused 
together, lies behind and somewhat below the visceral ganglia, is con- 
nected with the latter by two short, thick commissures, and sends off 
four nerves. One of these has already been described under the right 
visceral ganglion. The central nerve (23) is the longest and inner- 
vates the pericardium, aorta, part of the genitalia, the rectum, diges- 
tive gland and respiratory cavity. A somewhat shorter nerve on the 
right of this (22) furnishes nerve force to the posterior part of the 
aorta and a part of the genitalia. To the left of the central nerve a 
small nerve, arising apparently at a point between the abdominal and 
left visceral ganglia, supplies the anterior part of the mantle (21). The 
nerves of the abdominal and visceral ganglia also innervate different 
portions of the digestive system. 
In a living specimen the ganglia are of a very bright orange color, 
and in alcoholic specimens they are yellowish or yellowish white. The 
eyes are as usual in androgynous Pulmonata. The sclerotic membrane, 
choroid, cornea, etc., are well developed, and the optic nerve is very 
large. 
In working out the foregoing Lacaze Duthiers’ article in Archiv. 
de Zool. Exp., has been followed as a guide. The nervous system of 
the present species may be said to be almost identical with that of 
Lymnea pereger described and figured by Lacaze Duthiers (pl. 17, 
fig. 2). Spengel’s figure of Lymnea stagnalis is also the same (taf. 
xvi, fig. 11), excepting that the nerves to the penis and vagina are 
not shown. Moquin Tandon’s figures are different, his Lymnea palus- 
tris (pl. 34, fig. 27) showing a fused condition of the abdominal and 
visceral ganglia. In his figure of Lymnea auricularia the pleural and 
visceral ganglia appear to be fused and the nerves are insufficiently 
shown. No figures, excepting those of Lacaze Duthiers’, show the 
innervation of the male and female genitalia. 
The special organs of sense in Lymnea are those of TOUCH, SIGHT, 
SMELL and HEARING. The ORGANS OF TOUCH are the flat, triangular ten- 
tacles which may be repeatedly observed performing this function. 
The ORGANS OF SIGHT are the eyes which are well developed. Noth- 
ing definite is known concerning the powers of sight in the fresh-water 
pulmonates. Many Lymnzas are known from experiment to love the 
