STUDIES ON THE TURBELLARIA. 44] 
mouth-pieces and a series of rounded bodies, which | will 
term bulbs, with one of which each of the chitinous pieces is 
connected. 
From the irregular channels into which the lumen of the 
duct is divided a narrow canal (fig. 17, d.) runs to the base 
of each bulb, and, passing through it, enters the correspond- 
ing mouth-piece, through the axis of which it is continued to 
the free extremity. ‘lhe canal is dilated (d.’) immediately 
below the base of the mouth-piece, and sometimes, though 
rarely, there is a second dilatation further back. 
The structure of the bulb (fig. 18) is exceedingly difficult 
of determination, owing to its being nearly always packed 
full of sperms. In the few cases in which this was found not 
to be the case, it had a shrivelled appearance. It must have 
a bounding wall preventing the escape of the sperms and 
maintaining its regular form, and internally it appears to be 
of the nature of a sponge. Mark’s view that it is formed of 
greatly vacuolated and fused cells seems to me to be highly 
probable. ‘The chitinous mouth-piece is attached to it by a 
number of fibres, which run from the basal part of the mouth- 
piece into the substance of the bulb. ‘I'he spaces in the bulb 
must communicate freely with the canal as it passes through, 
to enable the sperms to be received, and to be afterwards 
discharged. 
The chitmous mouth-pieces (fig. 18, ch.) are, on the 
whole, very similar to those of Amphicherus and Poly- 
cherus, as described by von Graff and Mark. Lach is a 
slender cylindrical rod, tapering towards the extremity, and 
more or less strongly curved. Its chitinous wall consists 
of a large number of minute pieces (figs. 19 and 20), which 
are not rings, or perforated discs, as they are stated by von 
Graff to be in the species which he examined, but form each 
a little less than half a ring. 
As the mouth-piece tapers towards its free extremity the 
chitinous segments undergo a corresponding reduction in 
size. Besides being enclosed by these chitinous bodies the 
fine canal has a wall of its own, and at the free extremity 
voL. 49, paRT 3,—NEW SERIES, 32 
7 
