528 
HENRY LESLIE OSBORN 
excretory chamber (exp. of fig. 3). This is seen in all the cross 
sections occupying a position in the centre of the section, it is 
of varying diameter and in places measures 0.05 mm., equalling 
fully a third of the entire diameter of the body at the same level. 
That this chamber is not merely a space among the other organs 
is clearly indicated by the existence of a definite wall, seen in sec- 
tions as a thin sharp line, in which nuclei are distinctly recogniz- 
able, and of which surface views are also obtainable. Fig. 3 
includes a view of the organ seen on its surface posteriorly and in 
its lumen anteriorly. The boundaries of cells cannot be found 
in the wall and the line in not a double one but the relation of the 
nuclei warrants the belief that a definite cellular wall exists. In 
surface views the wall is a faintly stained finely grained film. In 
this film there are a few widely separated muscle fibres {ml in 
fig. 3), which are very clearly a part of this organ. Moreover, 
the living organ possesses the power of contraction. In living 
adults under observation I have seen pulsations taking place in 
this wall and discharges of granular material passing out of the 
terminal pore. 
Anteriorly on the level of the front of the ovary this tube forks 
where it reaches the bar formed by the oviduct and the two 
branches pass on forward till they reach the level of the pharynx. In 
living worms these branches are very conspicuous as clear spaces 
much lighter than the surrounding organs. 1 have tried to give 
this effect in figs. 1 and 2. In life these excretory cavities possess 
a smooth surface and, seen in profile, a sharp boundary. This 
makes it look as if there were a definite wall, but in views on sec- 
tioned material a wall cannot be recognized. In sections which 
show such clear evidence of a structural wall in the posterior 
cavity, as we have in fig. 3, there is no evidence of a similar wall 
or of any wall at all in the anterior cavities. The conclusion 
which we are forced to draw from this fact is that the anterior cav- 
ities are merely intercellular spaces permanent in position but 
not supplied with a definite wall of their own. The outer parts 
of the excretory system are thus more highly developed than 
the inner parts : or the anterior may be considered more embryonic 
than the posterior. 
