32 
margin, or slightly nearer the acetabulum, is situated the genital 
pore, which is rather prominent and is surrounded by darkly stain- 
ing tissue. 
Excretory pore. — The excretory pore is dorsoterminal. 
INTERNAL ANATOMY, 
Digestive tract.— The digestive tract is the most prominently 
developed organ system in this stage of development. Through its 
entire extent its lumen is entirely occupied by a gelatinous or (?) 
granular mass, in which cellular structure is not distinguishable. 
Extending dorsocaiidad from the oral sucker the esophagus may 
be distinguished ; at the point where the esophagus leaves this sucker 
there is a bulbous structure, the wall of which is composed of a single 
row of nucleated cells ; the impression gained is that this is a phar- 
ynx in process of development. The bifurcation (into two intestinal 
ceca) occurs about 56 /.t caiidad of the center of the oral sucker, so 
that the postpharyngeal portion of the esophagus, though distinct, is 
exceedingly short. In their course caiidad the intestinal ceca diverge 
from the median line and at first, for a distance of about 92 ,a, 
increase gradually in diameter; then they increase rapidly in diam- 
eter, but upon nearing the region of the genital pore they again 
decrease, each ending in a rather sharp point somewhat caudad of 
the pore ; in some cases they extend to a plane about halfway be- 
tween the genital pore and the caudal end of the body. In trans-. 
verse section the ceca are nearly circular, but the dorsoventral diam- 
eter is slightly greater than the transverse diameter (88 to 76 u 
in one case). Thus the ceca represent the two fusiform spots seen 
in the unstained specimen. 
In the wall of the ceca may be seen a few very small nuclei. 
The ceca are somewhat nearer the dorsum than the venter. 
Genital system. — The primordium of the genital system is present, 
but the arrangement of the sexual glands can not be analyzed. On 
section a distinct canal is seen to run almost directly dorsad, but 
slightly caudad, between the intestinal ceca d in one section this 
canal had the aj3pearance of dividing into two canals, a male and 
a female duct, but this point can not be asserted without reserve. 
The canal is surrounded by a mass of darkly staining tissue, about 
69 long (i. e., dorsoventrad in reference to the worm) by 46 fx 
broad (cephalocaiidad in reference to the worm) ; the entire structure 
gives the impression of being a cirrus pouch in course of development. 
Dorsocaudad of this structure is a second, much smaller, darkly 
staining mass of cells, and still further caudad, near the caudal mar- 
gin of the worm, is still a third darkly staining mass. 
