NATURAL HISTORY OF THE SHIP-WORMS, 223 
the branch of the so-called osphradial nerve from the visceral ganglion to the anterior 
ganglion is much larger than the nervous elements received by the anterior ganglion 
from the cerebro-visteral connectives. Pelseneer seems not to have seen the other 
nerves that leave the anterior ganglion. With as much reason it might be said that 
the structures they supply also are innervated from the cerebral ganglia. Nerve fibers, 
it may be, pass from these structures through the anterior ganglion to the cerebral, 
but that the latter are the only centers in which reflexes may be established seems 
not in accordance with the structure of the nervous system in Teredo. It seems 
more plausible to regard the anterior ganglion as a part of the visceral which has 
been separated from the latter. It receives a part of the cerebro-visceral connective, 
and gives off some of the nerves that formerly were given off by the visceral. 
From a theoretical standpoint, too, one would expect elongated forms like 
Teredo and Pholas to have a more direct connection between the osphradia and the 
reflex centers. If the osphradia test the character of the water flowing over the gills, 
then it is difficult to believe that in a large ship-worm the nervous impulse should 
travel from them to the cerebral ganglia and back again through the visceral ganglion 
to the pallial nerves before the siphons can be contracted and the inhalent current 
stopped. This would necessitate a course of almost two meters in very large speci- 
mens. The more direct connection through the visceral ganglion is the one it seems 
reasonable to expect. 
KIDNEYS. 
The kidneys (organs of Bojanus, nephridia) of Teredo were observed, apparently, 
by Deshayes, but mistaken for veins. Quatrefages also observed them, but gave 
no adequate description. Pelseneer (1891) has noted the position and relations of 
the openings of the two ducts. 
In the adult ship-worm the paired kidneys lie on the dorsal side of the large 
pericardial cavity and ventral to the anal canal, extending through the long distance 
between the posterior adductor muscle and the visceral ganglion. Each kidney 
consists of what may be termed the body, which lies around the posterior face of the 
posterior adductor muscle (/, fig. 10), and two very long ducts, one of which puts 
the body of the kidney in communication with the pericardial cavity, while the 
other leads to the exterior. The body is a massive, much pouched structure, in 
which the lining secretory epithelium is vacuolated and in part ciliated. From 
the body the very long, narrow, cylindrical afferent duct passes posteriorly (ka, fig. 
27-29) near the midline. Just in front of the visceral ganglion it enlarges, becomes 
convoluted internally, diverges from its fellow of the opposite side (k a, fig. 62), and 
dips under the end of the efferent duct (fig. 61) to open into the posterior angles of 
the pericardial cavity (fig. 30) by a large funnel-shaped opening. The lining cells 
of the afferent duct are not vacuolated and apparently not excretory; and not 
ciliated except in the enlarged, funnel-shaped portion, in which they bear strikingly 
long, dense cilia (fig. 64). 
The efferent duct, leading from the body of the kidney to the exterior, is also 
a cylindrical tube, of much larger diameter than the afferent duct. It runs with 
the latter near the midline (ke, fig. 10, 27-29), and in front of the visceral ganglia, 
after diverging slightly from its fellow of the opposite side (fig. 62), it crosses dorsal 
