PROBOSCIS OF SYLLIDEA 335 
through the substance of the wall ; but. the chief space is taken 
up by the epithelium modified into a mass of gland-cells similar 
to those composing the anterior proventricular glands. They 
are apparently syncytial, and in most specimens present the 
appearance, in the aggregate, of a mass of sinuous and anasto- 
mosing tubules and vacuoles with thin walls and without distinct 
contents: more rarely the spaces are filled with a secretion 
capable of taking a strong stain with haematoxylin. In the 
Kxogoneae the‘ ducts’ from this mass of unicellular glands 
do not seem to open—in great number at least—into the cavity 
of the ventriculus itself, but run forwards to open into the 
recess at the extreme posterior end of the proventriculus. It 
is in very few preparations that this destination is traceable : 
the specimen must happen to have been fixed when the secre- 
tion was actually being discharged, and the strands of secretion 
by which alone the course of the ‘ ducts’ is traceable, must 
have become differentially stained. In the other sections of 
the Syllidea I have not been able to trace this connexion, 
and I am led to conclude it is not universal. 
VIII. Tur Post-vENTRICULUS. 
Sharply marked off both from the ventriculus m front and 
the intestine behind is the chamber from which are given off 
laterally the two caeca present in most of the Syllidea 
with the exception of the Autolytea. 
This, as already noticed, is recognized as a separate chamber 
by Hisig, and he gives prominence to it as the second main 
division of the alimentary canal—the first bemg the whole 
proboscis-oesophagus (Riisselésophagus) and the third the 
intestine. De Saint-Joseph, on the other hand, and Malaquin 
do not recognize the distinctness of this chamber from the 
proventriculus. Its walls have only a thin layer of muscle ! 
without radial fibres. Its epithelium is ciliated and is loaded 
1 It may be pointed out here that Malaquin was in error in stating that 
the intestine is devoid of a muscular layer. There isa thin layer of flattened 
fibres, not placed in close contact with one another, composed of outer 
longitudinal and inner circular elements, 
