MONILIGASTER GRANDIS, A. G. B. 319 
septum is made up of fibres crossing one another in all direc- 
tions. Where the septum joins the body-wall the centripetally 
placed fibres spread out and penetrate to a certain extent the 
longitudinal muscular layer of the body-wall. In the case of 
the septa in the hinder region the same sort of thing occurs at 
the junction of the septum with the intestinal wall, indeed, 
close to the intestinal wall the septa become so thick as to 
almost join one another along the intestinal wall. 
ALIMENTARY TRACT. 
It is, so far as I can see, impossible to say with certainty 
from an examination of the adult worm, to what segments the 
anterior portions of the alimentary canal really belong. In 
front of Septum v-vi, i. e. in the five most anterior segments, 
lie the buccal region, the pharynx, and a considerable length 
of csophagus. From the arrangement of the nephridia and 
blood-vessels I should say that this latter occupies, at any 
rate, Segments 111, Iv, and v; this leaves Segments 1 and 11 
only for the buccal region and pharynx. Longitudinal sec- 
tions show a slight change in the character of the alimentary 
epithelium at the posterior limit of Segment 1, so that I think 
we may assume that the buccal region occupies this segment 
while the pharynx is confined to Segment 11. The pharynx 
extends backwards, of course, far beyond the limits of this 
segment as marked by the grooves on the body-wall, but these, 
as we know, by no means determine the true anatomical posi- 
tion of an organ. 
The buccal region is completely eversible and can be pro- 
truded with the prostomium (fig. 16), or it can even be pro- 
truded while the prostomium remains completely withdrawn. 
The pharynx is comparatively thin-walled except in the 
dorsal region. When the pharynx is cut open ventrally a 
circular portion of its dorsal wall appears as a thick pad, while 
a circular wall stands up all round this. This pad can be pro- 
truded, and forms the piston which is used in sucking in 
the earth and in excavating the burrows (fig. 17, m.). Numer- 
ous strong muscles run from the outer wall of the pharynx to 
