STRUCTURE OF THREE NEW SPECIES OF EARTHWORMS. 109 
lium. The outermost epithelium consists of delicate flattened 
cells (fig. 6, p .) ; the perihsemal space is lined by rounded cells 
which are aggregated here and there into clumps (fig. 6, p.). 
I was at first inclined to regard these cells as free corpuscles 
which had become adherent to the walls of the perihsemal 
space ; the fact, however, that these cells were invariably, 
so far as my experience goes, attached to the periphery 
of the perihsemal space, not to the periphery of the con- 
tained blood-vessel, seemed to show that they are the peri- 
toneal lining of this section of the coelom. It seems certain 
that the cells are in a state of energetic proliferation, and it is 
possible that in this perihsemal space — and from its lining 
cells — is carried on the formation of the coelomic corpuscles. 
The blood-vessels themselves are covered by a single layer of 
large cells ( p ".) filled with yellowish-brown granules. Some of 
these cells appeared to be multinucleate, and there is some 
variation in size. 
The enclosure of the dorsal blood-vessel in a special coelomic 
sac suggests of course the pericardium of higher types, and in 
any case it may be compared with the condition of the coelom 
in the Hirudinea, where the principal blood-vessels as well as 
other organs are often included in separate coelomic spaces. 
Among the Chaetopoda also a commencement of a secondary 
subdivision of the coelom is to be seen. In the Capitellidse a 
series of longitudinal chambers enclose the nephridia and other 
organs; but I am not aware that hitherto anything of the kind 
has been described in the Oligochseta. 
Reproductive Organs. — The vesiculse seminales oc- 
cupy segments 11 and 12; they are racemose organs like those 
of Acanthodrilus. The testes I have not seen. 
The vasa deferentia open by funnels in segments 10 and 
11; the funnels of segment 11 are quite independent of the 
vesicula. I could not trace the course of the vasa deferentia ; 
but in all probability they open, as in Acanthodrilus, upon 
the eighteenth segment. 
The atria are in segments 17 and 19; the external aper- 
tures of these organs have been already mentioned. The atria 
