NEW RHABDOCCELE COMMENSAL WITH MODIOLUS 375 
transition from the esophagus to the intestine is not abrupt. In 
the case cited it maintained about the same diameter for a dis- 
tance of 0.05 mm., then widened rapidly for about the same dis- 
tance into the intestine (fig. 4). 
The intestine extends to the posterior end of the body. Its 
position is dorsal. In life the cells that line its cavity seem to be 
rather loosel}' attached. They are usually yellowish or yellow- 
ish-green, especially in the older individuals. Rudiments of the 
esophagus and pharynx were noticed in young individuals that 
were still in the embryonic capsules. The intestine is usually 
rather difficult to see in the living specimens In one instance it 
was plainly seen as a thin walled elongated sac extending nearly 
to the posterior end. It was filled with yellowish granules sus 
pended in a fluid, and the contents were kept moving backward 
and forward by the contractions of the body. The specimen 
being under slight pressure, some of the intestinal contents were 
pressed out of the mouth. 
Male genitalia 
I have not yet been able to make out the anatomy of the geni- 
talia with entire satisfaction. This apparent indefiniteness of 
the genital organs may indeed be incident to the viviparous con- 
dition, which may, in turn, be seasonal and parallel with the pro- 
duction of summer eggs as has been shown to be the case with 
some of the Mesostomata. It is more probable, however, that 
the species is protandrous. 
The genital pore is ventral and approximately at the anterior 
third or fourth. In one specimen which, flattened under the 
cover-glass, measured 2 mm. in length, the genital pore was ap- 
proximately 0.06 mm. from the anterior end. In another, meas- 
uring 1 mm., it was 0.25 mm. from the anterior end. Sections 
show that the pore communicates with a subglobular or pyriform 
sac which contains spermatozoa. These were seen in active 
motion within the sperm-sac in living specimens. There is a 
short penis which lies like a plug in the duct leading from the 
