CASTLE: NORTH AMERICAN RHYNCHOBDELLID&. 27 
tinues backward through the brain mass, ending in somite xu. (Figure 1). 
Within the pharyngeal sac lies the proboscis (pr’b., Figure 1), which, in a state 
of rest, usually extends from a point just behind the brain back into somite 
x1I., where the ducts of the salivary glands enter its walls. These glands 
(gl. sal., Figure 1) are a conspicuous feature of a Glossiphonia differentially 
stained. They are always unicellular, and represent the largest cells found in 
the body except certain nephridial cells and eggs approaching maturity. The 
salivary gland cells have a great avidity for stains. They number in this 
species thirty or more in each half of the body, and are found scattered through 
about three somites (x1.-xtv.). The largest gland cells are those most remote 
from the base of the proboscis. Each cell has a separate slender duct leading 
into the wall of the proboscis and opening into the lumen of that organ at 
some point along its length. 
A short slender esophagus (@., Figure 1), ordinarily lying entirely within 
somite XIII., connects the base of the proboscis with the crop (vglv., Figure 1). 
This readily distensible part of the digestive tract extends over six somites 
(xtv.-x1x., Figure 1). Under ordinary circumstances it has but a singie pair 
of lateral diverticula ; these arise in somite xIx. and extend backward, usually 
ending in somite xxi. After a full meal, however, short lateral diverticula 
may sometimes be seen also in the five more anterior somites (XIV.-XVIII.), 
but this condition appears always to be a transient one. 
The stomach (ga., Figure 1) begins in somite xx. and ends in somite XXIII. 
It bears four pairs of persistent lateral diverticula doubtless originally seg- 
mental in origin, but now crowded within the limits of about three somites. 
The first two pairs of stomach diverticula are directed forward, the last pair 
backward ; the third pair lies about at right angles to the long axis of the body. 
The terminal part of the digestive tract, the intestine (in., Figure 1), is a 
gradually narrowing tube; it includes one or two proximal chambers separated 
from the following part by constrictions. 
The anus is dorsal in position, as in all other leeches, and lies within or just 
behind somite xxvil. (Figure A, page 32; Figure 34, Plate 8). Comparison 
with other species, in which the reduction of somites is less extensive, shows 
that primitively the anus lay behind somite xxvil. 
Jj. NEPHRIDIA. 
The nephridia number at least sixteen pairs, possibly seventeen pairs. The 
nephropores (nph’po., Figure 4) lie on the ventral surface of the body, somewhat 
nearer the margin than the median plane, and almost exactly in the middle of 
their respective rings. The nephropores are always found in this genus on the 
middle ring of a somite. I have found them in sections of G. stagnalis in 
somites VIII.-XXIV., with the single exception of somite x11. (ring 28). The 
strong development of the salivary glands in this region may account for the 
possible disappearance of the pair of nephridia which we should expect to 
find here. 
