IOWA ACADEMY OF SCIENCES. 
179 
often be traced into contact with the otocyst, but I have been 
unable to demonstrate actual connection with this or with 
fibres from the cerebro-pedal commissure. Regarding the 
function of otocysts see Dr. Brooks’ article (No. 1). 
CIRCULATORY SYSTEM. 
The heart, Figs. 1 and 5, consisting of a single median 
ventricle, v t, and a pair of lateral auricles, a u, lies in the per- 
icardial cavity, near the dorsal surface of the animal, and 
somewhat in front of the posterior adductor muscle. All the 
blood channels issuing from the ventricle are without very 
definite walls or calibre. Immediately in front of the peri- 
cardium the blood channel, Fig. 1, which leaves the heart in 
this direction, divides. The larger branch is continued for- 
ward along the dorsal line of the body, turns to the left and 
passes beneath the oesophagus, which it follows to the mouth. 
When opposite the dorsal end of the anterior adductor muscle, 
a branch is given off which passes in front of the adductor and, 
dividing, sends a branch to each mantle lobe. The main chan- 
nel is continued down in front the cerebro-pedal commissures 
into the foot, where it divides into a number of small branches 
that apparently ultimately end in the connective tissue spaces 
with which the whole body is permeated. The smaller branch, 
which arises immediately iu front of the pericardial cavity, 
passes downward, sends a branch to either side of the stomach, 
supplying that organ throughout its length with small 
branches, and finally ends among the loops of the intestinal 
coil. 
Posteriorly the ventricle gives rise to a channel of consider- 
able dimensions which surrounds the intestine, but is more 
spacious beneath than above it. Tne intestine seems to be 
held in the dorsal part of this channel by strands of connective 
tissue. Behind the posterior adductor muscle this channel 
widens on opposite sides of the intestine and is continued into 
the mantle lobes. It is not improbable that other important 
channels exist. Fig. 5 is a section across the body in the 
region of the heart showing the connection that exists between 
the auricles and the blood spaces of the gills. 
ORGANS OP BOJANUS. 
The organs of Bojanus consist of a pair of coiled and saccu- 
lated tubes, one on each side of the body, lying between the 
pericardium and the posterior adductor muscle. At one end 
