INTERNAL ANATOMY. 343 
delicate branch to the peritoneum, another, 2b/, branching to the distal end 
of the large hermaphroditic duct and to the peritoneum of the vesicle of Swam- 
merdam, and then bifurcates equally. One of the branches thus formed, 2b4, 
curves to the left and upward around the anterior border of the adnexed genital 
mass and penetrates the dorsal body-wall above the latter. Here it gives off 
slender branches to the vesicle of Swammerdam and to the peritoneum. The 
main trunk penetrates among the muscles forming the floor of the pericardial 
cavity, courses obliquely backward to its posterior wall, in which it again ascends 
to recurve obliquely to the right in the roof of the pericardium. It innervates 
the floor of the pericardium, the anterior end of the crista aortae, the beginning 
of the auricle, the roof of the pericardium, the reno-pericardial opening and 
its tube, and the kidney. The other branch, or genital nerve, 2b3, passes directly 
backward and across the base of the adnexed genital mass to the genital ganglion 
group, g.g.- This latter complex is shown on Plate 6 in fig. 4, g. g, and in more 
detail on a larger scale in fig. 1 of the same Plate. Here the delicate con- 
nective-tissue investment of the distal end of the small hermaphroditic duct has 
been dissected away, exposing the whole group of genital ganglia. Two of 
these, gi and g2, are fairly conspicuous (Plate 5, fig. 4), but the remaining 
ones, g3 and g4, require careful dissection under high magnification for their 
detection. The genital nerve, g.n, the branch of the second visceral nerve just 
described, terminates in the largest of these genital ganglia, g/, from which the 
nerves, a, pass into the adjacent dorsal peritoneum, and the nerve, b, is sent to 
the small hermaphroditic duct. The remaining ganglia, g2, g3, and g4, are con- 
nected with gi in a complicated plexus from parts of which the nerves, c, pass on 
to the small hermaphroditic duct and the ovotestis, while the fine branches d, 
together with other still finer ones not figured, penetrate the adnexed genital mass. 
Figure 1 of Plate 3 illustrates the parieto-visceral complex of Tethys cervina, 
as described by the writer (1909). It is here introduced to call attention to the 
homologies existing between this representative of the Aplysiinae and Dola- 
bella agassizi. Comparing this with Plate 3, fig. 2 it is seen that the two visceral 
nerves in Dolabella represent the four shown in Tethys cervina, the second one 
in Dolabella being formed by the union of the second, third, and fourth of 
Tethys. Identical relations in the visceral innervation of the organ of Bohadsch 
and in the anastomosis of a branch of the second visceral with a pedal nerve 
are also evident, so that the double innervation of this organ from both visceral 
and pedal ganglia obtains in this subdivision of the family Aplysiidae, as well 
as in the more restricted Aplysiinae. 
