468 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
the tube. The last, posterior one, passes much beyond the limits 
of the tube and then is but a narrow groove in the exoskeleton, of no 
use as a direct exit for sperm. In the same way the plane anterior 
to the last passes posteriorly on the right, much beyond its opening 
into the tube. 
Only the anterior end of the recess appears to open into the plane 
leading to the suture and sperm would have to pass into the bulb or 
else into the suture plane where the latter is the outlet for both bulb 
and recess. The posterior part of the recess was without any direct 
outlet though this seems to vary in different specimens. 
It is evident that the annulus of C. bartoni admits of the same inter¬ 
pretation as that given for the other species. It is a sperm-storage 
pocket though a simple one and not much bent. Unlike the others, 
much of its course is transverse and its orifice is far to one side of the 
median plane. 
Here again all individuals are not alike in their symmetry but some 
may be called right- and the others left-handed. In the former cases, 
as above figured, the orifice was on the animal’s right. In the latter, 
the orifice was upon the animal’s left and the whole curve of the trumpet 
the reverse of the other case, so that one of the above figures looked at 
through the paper from behind would represent a left-handed annulus. 
Of twelve females examined, eight had the orifice upon the animal’s 
right and four upon the left so that this right-handedness was the rule 
among these specimens. 
Structure in Cambarus immunis .— One hundred small specimens 
were sent me in October from the pond in Michigan whence Professor 
Herrick (’ 95 ) obtained eggs in early stages, November 16, 1893. Some 
paired October 11, and on November 21 two females, 49 and 54 mm. 
long respectively, were carrying eggs in an early larval stage after 
cleavage. The habits of the males seen transferring sperm seemed to 
be the same as in C. affinis and 0. virilis. 
Many of the survivors cast their exoskeletons in April and when 
studied in May the annuli naturally showed no trace of sperm. 
The annulus in these specimens was small and inconspicuous. It 
had the triangular form represented in figure 45 (pi. 48) and was soft 
and delicate and excepting the posterior border, was translucent before 
clearing in oil of cloves. 
The posterior border is a marked elevated transverse rounded ridge 
that is lower at the middle line so that a posterior view of the annulus 
