CONTRIBUTIONS TO THE ANATOMY OF EARTHWORMS. 447 
quite independent up to their point of opening into the 
atrium. The atrium is double, but the two halves are enclosed 
in a common muscular sheath, and present no external evidence 
of their separation; distally the cavities of the two atria join 
to form a common duct, with thick muscular walls and lining 
of non-glandular epithelium. This duct passes into a penis, 
which is a projection of the body wall lodged in a pouch-like 
depression of the integument; acushion-like thickening of the 
walls of this latter (“bursa copulatrix,” Perrier) bears the 
orifice of a pair of short cecal tubes, dilated at the cecal 
extremity ; these are lined with a cubical epithelium and have 
thick muscular walls. Sometimes the free extremities of the 
two tubes unite, and they then form a single horseshoe-shaped 
tube. 
I have elsewhere pointed out that the atrium, into which the 
vasa deferentia open, is probably equivalent to the “ prostates ” 
of other Earthworms, its resemblance in minute structure to 
the prostate of Acanthodrilus being very ciose; and the 
bursa copulatrix is not represented in any other Earthworm, 
but would seem to be equivalent to the penis sheath of the 
Tubificide ; the penis itself in Eudrilus appears to be fixed 
to the body wall within the bursa copulatrix, and not to be in- 
or evaginable; its protruded condition, which, so far as my 
experience goes, is invariable, may, however, be possibly due to 
contraction, caused by the killing fluid. The “ y-shaped 
appendage,” which opens on to a sensitive (?) pad near to the 
penis, has puzzled M. Perrier as well as myself. The cha- 
racter of its epithelium seems to negative the possibility of its 
being a gland. The only structure with which I can compare 
it is to the sacs of penial sete which occur in so many Earth- 
worms. I find that the dorsal pairs of setee upon the segment 
bearing the male generative pores are absent, the position of 
the pores being a little behind that which would normally be 
occupied by the sete. The structure of the sac is certainly 
rather different from that which encloses the penial sete in 
other Earthworms ; but Stolé has figured (38, pl. iii, figs. 15, 
16), attached to the spermathece of Psammoryctes bar- 
