M, The water - pore, leading by the stone - canal stc to the waterring, from which hangs a Polian vesicle pb.
The statocysts present in general the structure of either a knob or a closed vesicle, composed of (I) indifferent supporting epithelium; (2) sensory, so-called auditory epithelium of slender cells, each.
Bergh (for Lumbricus and Criodrilus), whose figures show a derivation of the entire nephridium from mesoblast, and an absence of any connexion between successive nephridia by any continuous band, epiblastic or mesoblastic. A midway position is taken up by Wilson, who asserts the mesoblastic formation of the funnel, but also asserts the presence of a continuous band of epiblast from which certainly the terminal vesicle of the nephridium, and doubtfully the glandular part of the tube is derived.
Each testis communicates by means of an efferent duct with a common collecting duct of its side of the body, which opens on to the exterior by means of a protrusible penis, and to which is sometimes appended a seminal vesicle.
In the New Britain species the egg is still smaller (I mm.), and there is a large trophic vesicle.