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Transactions of the Boyal Society of South Africa. 
development of the brood pouch brings about a remarkable tenuity of the- 
body wall and a displacement of the organs to the dorsal and dorso- 
lateral regions. 
The musculature of the body wall is typically developed in the regions 
anterior and posterior to the brood pouch, but the ventral wall of the 
brood pouch has a much smaller development of muscles than the dorsal. 
However, this ventral wall is clearly seen to be the original, or rather 
primitive, ventral wall, the muscle fibres being continuous with those of 
the anterior and posterior regions. The dorsal and lateral walls of the 
pouch, however, are devoid of any musculature comparable with the 
transverse and longitudinal muscles of the body wall. The internal lining 
layer of the pouch consists of an irregular and generally indistinct epithe- 
lium which grades into a faint musculature in parts. 
The greater portion of the dorsal and lateral regions of the body in the 
vicinity of the pouch is occupied by the digestive and sinus systems. 
In the anterior and posterior parts of the body structures which agree- 
in their disposition with the limits of the somites as mapped out from 
external studies are developed which apparently correspond to septa, and 
these give great assistance in mapping in the distribution of the various 
organs with reference to the somites, which would otherwise be impossible 
owing to displacement caused by the great development of the pouch. 
It is clear that the pouch has not been formed by an intensification of 
the condition found in other Glossiphoniidae where a temporary pouch is 
formed by an inflection of the edges of the body ventrally, but is a specially 
developed structure, as is clearly shown by the nature of the dorsal and 
ventral walls, each of which shows no musculature other than that 
characteristic of their respective superficies in other Glossiphoniidae. 
The pouch occupies the position which is taken, at least ventrally, by 
the large sac-like ovaries of other Glossiphoniidae, and it is highly prob- 
able that the dilated portions of these sacs have lost their germinal 
function and become united to serve as a brood pouch. This idea is- 
supported not only by the position of the pouch, but also by the paired 
nature of the poach as indicated by the anterior and posterior horns. 
This has led to a restriction of the germinal area to the anterior portion 
of the ovary as it is found in other Glossiphoniidae, and also to a displace- 
ment of the same forwards by the growth of the pouch. 
Alimentary Canal. — This structure is divisible into the same regions as. 
that of other Glossiphoniidae. 
The proboscis extends backwards as far as somite xi, nearer the dorsal 
than the ventral side of the animal. The oesophagus then passes upwards 
and backwards over the vesicula seminalis and in somite xiii descends 
behind that structure to pass into the ovary. In the posterior region of 
xiii it emerges from the ovary and then again ascends obliquely backwards- 
