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segments. They are placed at the posterior margin of the 
ring which succeeds the second and third chetigerous 
annuli. Between the first and second diaphragms 
there are dorsal and ventral mesenteries* supporting the 
corresponding blood-vessels; the dorsal mesentery 
terminates in front about the level of the posterior margin 
of the first cheetigerous annulus. The funnels of the 
first pair of nephridia perforate the third diaphragm, and 
le on its anterior face. Behind this diaphragm the body 
is uninterrupted by septa almost to the base of the tail, 
but rudimentary septa may be recognised as strands of 
connective tissue accompanying some of the afferent and 
efferent vessels connected with the nephridia and gills. 
Towards the posterior end of the gill region this tissue 
increases in amount so as to form in the last, or last two, 
gill segments an almost complete septum. 
It will be seen that all vessels connected with the 
stomach are attached to its ventral face. This arrange- 
ment, together with the absence of mesenteries from this 
region, allows considerable freedom of motion to this part 
of the gut without endangering the blood-vessels which, 
by their length and flexibility, appear to readily permit 
this motion. During digestion the stomach is swung 
backwards and forwards by movements of the body, and 
the arrangement of the blood-vessels indicates a con- 
siderable amplitude of swing. There is, however, a 
structure which probably acts as a sort of safety cord to 
prevent the backward motion becoming so great as to 
rupture the vessels. This is a solid pinkish cord of con- 
nective tissue, which may easily be mistaken for a vessel ; 
it is attached ventrally to the anterior wall of the stomach, 
lies alongside the afferent vessel of the fourth nephridium, 
* The ventral mesentery also runs backwards through a con- 
siderable part of the third chetigerous segment. 
