STRUCTURE OF THREE NEW SPECIES OF EARTHWORMS. 125 
is only a single male pore situated on the eighteenth segment 
(see above, p. 102). 
Ocnerodrilus (Eisen 12) offers an interesting parallel. In 
this Annelid there is a saccular body opening in common with 
the vasa deferentia, which is probably, as Yejdovsky has sug- 
gested, the atrium. 
There seems, indeed, to be little doubt that the so-called 
prostates in these types are (i) homologous with each other, 
and (ii) are homologous with the atria of the aquatic forms. 
A gradual series of transitions unites Eudrilus, which is the 
least modified, with Acanthodril us, which stands perhaps 
at the other extreme. It is possible that the division of the 
atrium in Eudrilus (Beddard 6) bears some relation to the 
double atria of Acanthodrilus, but I have not yet 
thoroughly investigated this point. The term “prostate” 
must therefore be no longer applied to these glands. 
The racemose glands of Perichseta, &c., now remain for 
consideration, and the question which must be answered is : 
Are these glands the homologues of the prostates of the 
Tubificidse, or do they correspond to the atria of Eudrilus 
and Acanthodrilus? 
The structure of these glands is as follows: — They consist of 
a series of branching ducts, lined with a single non-ciliated 
cubical epithelium ; the ducts appear to end blindly, but groups 
of glandular cells are attached to them here and there, and 
doubtless void their secretion into the ducts. The ducts unite 
into a main duct, which opens in common with the vas deferens 
into a thick-walled muscular tube, which, at least in Peri- 
chaeta Houlleti, can be evaginated, and probably serves as a 
penis. The glandular cells are exactly similar in their struc- 
ture to the cells of the prostate in the Tubificidse ; they also 
resemble the glandular cells of the atrium in Pontodrilus 
(cf. PI. XIII, figs. 12, 13). At first sight, therefore, three 
hypotheses seem to be possible: either the whole structure 
corresponds to the atrium of Acanthodrilus, differing only 
in the branching of the cavity and in the segregation into 
groups of the glandular cells, or the ducts alone are collec- 
