714 Wisconsin Academy of Sciences, Arts, and Letters. 
mean and multiplying by 100, which gave 8.9905. A correla¬ 
tion table of length of animal with number of caeca showed 
that the number did not increase with age. The position of 
the caeca with reference to the other viscera is shown in Plat© 
XLI, Figures 1 to 8. This position determined two intervals in 
the circle of caeca. One bread interval, at one side of which 
the ductus choledochus enters the intestine, is caused by the 
stomach (Plate XLI, Fig, 7). The other interval on the 
right is caused by a loop of the intestine, the presence of which 
is constant. The first I propose to> call the gastric interval, 
and the interval on the right the enteric interval. Between 
these two intervals there is normally but one caecum. This I 
will call the pollical cue cum, from the analogy of its position 
relative to the other caeca with that of the thumb relative to 
the fingers. This caecum is seen from the right side extending 
parallel to, and dorsal of, the intestine. Very rarely, the polli¬ 
cal caecum is replaced by two caeca. This occurred four times 
in 229 individuals. One case is represented in Plate XLI, 
Figures 3, 4 and 5. Barely the pollical caecum, instead of ap¬ 
pearing dorsal of the intestine, is turned under the loop of the 
intestine so as not to be seen from the side. 
Although the relative lengths of the caeca in no two individ¬ 
uals agree, by averaging many individuals a definite relation of 
the lengths of the caeca of the different positions is shown. 
The length of the caeca is expressed in percentage of the length 
of the longest caecum in the individual. This was neces¬ 
sary, because in much of the material the total length of the 
animal was unobtainable. The lengths are graphically shown 
in Plate XLIV, Figure 1, when there are seven caeca, and in 
Plate XLIY, Figure 2, when there are eight caeca. There is 
a regular diminution in length from the stomach towards the 
ventral side on each side. A cause of this diminution is prob¬ 
ably to be found in the fact that the plane of their bases is not 
at right angles to the long axis of the fish, but inclines, with dor¬ 
sal caeca arising more cephalad. Since they all project cau- 
dad, those which arise nearer the back will have more space in 
which to grow before meeting an obstacle. This cause may be 
