236 Transactions of tJie Boijal Society of Soutli Africa. 
{h) The middle layer is composed of muscle fibres, oblique and circular 
in direction. 
(c) The outermost layer is composed of loose parenchyma-like cells 
which in places are very indistinctly made out. This is in all probability 
due to the state of preservation. 
The only other member of the Phreodrilidse possessing any structure 
resembling this sac is Phreodriloides, where we find a chamber into which 
the male pore and the spermduct lead. 
This structure has until now been imperfectly understood, since the 
absence of true spermathecae in Phreodriloides raised special difficulties. 
Benham termed it tentatively an " autospermatheca," or, at least, 
regarded the portion lying behind the entrance of the spermduct as 
corresponding to a specially developed spermathecal apparatus, rather 
than that the spermathecal pore had moved forwards and become 
coincident with the male pore. 
There can be no doubt that in the rejection of the latter explanation 
Benham was quite correct. 
The anatomy and histology of the form under description show clearly 
that the large chamber is nothing more than the greatly enlarged penial 
sheath. Its histology is fundamentally similar to the normal penial 
sheath of such forms as Astacopsidrilus and its relation to the penis 
corroborates this idea. 
The " muscular sac " of Phreodriloides is undoubtedly the homologue 
of the posterior horizontal portion of this sac in Gondwanaedrilus, and 
both of these structures are posterior outgrowths of the penial sheath. 
The so-called penial chamber of Phreodriloides and the "muscular sac" 
have become differentiated histologically along different lines, the former 
becoming in part glandular, the latter becoming heavily muscularised. 
Both, however, represent portions, ventral and dorsal respectively, of the 
large sac of Gondwanaedrilus. 
A glance at the figures of this structure in both genera will quickly 
convince one of the homology. 
Anatomically, special interest centres round the spermathecae and male 
reproductive apparatus since we now have a definite explanation of the 
peculiar modification of these in Phreodriloides. 
In order to make this perfectly clear we will orient ourselves by taking 
in assumption as normal the condition of these organs in Phreodrilus. 
In this genus the spermathecae are well- developed paired structures 
opening independently to the exterior, and provided with a strong definite 
granular and glandular epithelium. This applies to all the species of the 
genus. 
In Astacopsidrilus the spermathecae may remain separate or may 
430mm unicate with each other, but the walls retain the same nature of 
