The Morphology of Coeloplana. 53 
canals retain their tubular character throughout. The lining cells 
however are not distinct in character from those of the other species, 
except that being more confined, they are more regular in their 
arrangement (cf. Fig. 14). 
From the infundibulum there branch upwards two delicate tubes 
which open to the exterior in short papillae. As in the typical 
Ctenophores these arise in such a position that along the tentacular 
plane the lower one is to the right and the upper one to the left of 
that plane. These tubes appear to arise singly and a complementary 
blind ampulla in the alternate quadrant, such as is found in the 
Ctenophores, could not be demonstrated. 
Finer structure of the gastric system. 
The epithelium of the ventral face of Coeloplana is continued 
into the mouth, and lines the pharynx. In the latter regions, as 
noted above, the ciliated cells are large and the cilia heavier than 
elsewhere. The same kind of gland cells found in the body 
epidermis is also found in the pharynx, in all the various 
stages. The stomodaeal canal arising from the roof of the 
pharynx and leading upward into the infundibulum is lined 
with powerful cilia. The cells are columnar and very granular in 
all the preparations observed. The nucleus is often much enlarged, 
packed with chromatin granules and stains very densely. The cells 
of the infundibulum itself show the same structure as those of the 
canal. The cells lining the main branches of the canal system 
constitute a squamous epithelium. These thin walled tubes as they 
proceed toward the periphery and break up into finer subdivisions 
show marked changes in structure. The cells lining them elongate 
and the nucleus usually takes up a position in the basal end, — the 
tissue thus changing from a squamous to a stratified columnar 
epithelium. This gives place to a further differentiation, peripherad. 
The cells become greatly vacuolated, enlarge and bulge out in masses 
into the digestive canals. The respiratory tentacles being out- 
growths of the canals themselves, are lined with the same epithelium, 
reduced to a thin squamous layer. In the peripheral region various 
metaplastic bodies become very evident: globules of fat, staining 
densely with osmic acid, others that take anilin acid stains and 
still others that stain with basic dyes. In addition all varieties of 
ingested food matter may be found, such as diatoms, as well as 
other foreign bodies, apparently half digested. These vacuolated 
