The network is, however, of the duct of the nephridium, possibly ectodermic in origin, and does not affect the glandular tubes which remain undivided and with one coelomic funnel each.
The alimentary tube consists of three regions: firstly, the anterior buccal mass with the oesophagus, of ectodermic origin, and therefore bearing cuticular structures, namely the jaws and radula; secondly, the mid-gut, of endodermic origin and including the stomach and liver; and, thirdly, the hind-
Schepotieff (1907) states that in the young buds of the latter the central part of the alimentar y canal is developed from cells which are apparently not of ectodermic origin.
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