IOWA ACADEMY OF SCIENCES. 179 



often be traced into contact with the otocyst, but I have been 

 unable to demonstrate actuil 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 ihe 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 in 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. Tae intestine seems to be 

 held in the dorsal part of this channel by strands of connective 

 tissue. Behiad the posterior adductor muscle this channel 

 widens on opposite sides of the intestiae 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 conaection that exists between 

 the auricles and the blood spaces of the gills. 



ORGANS OF BOJANUS. 



The organs of Bojanus consist of a pair of coiled and saccu- 

 lated tubes, one on each side of Ihe body, lying between the 

 pericardium and the posterior adductor muscle. At one end 



