54 James Francis ABBOTT, 
cells also occur in the branches of the canal system that penetrate 
into the tentacle root and adjacent tissue (“tentacular canals”). 
There are no cilia in the canals and no evidence of a syncytium, 
— the cell outlines being always distinct. In certain regions these 
vacuolated cells proliferate in long strands or sheets, from the 
distal ends of which cells bud off (Fig. 32 and 39) which assume a 
spherical shape and float freely in the gastric canals. In C. willeyi 
this process is confined to the peripheral region of the body while 
in ©. mitsukurv’ it takes place in a region approximately midway 
between infundibulum and periphery. In all cases these cells contain 
a nucleus and sometimes more than one. The cytoplasm is densely 
granular and seemingly not at all different in structure from that 
of normal epithelial cells except that there are no metaplastic 
granules or ingested food material. Two or three are frequently 
clumped together. In some instances at least there is an envelope 
of small cells about a large cell. It may be that these smaller 
enveloping cells fuse together about the nucleus of the central one, 
and this too may account for the presence"of more than one nucleus. 
These cells are frequently vacuolated and the chromatin is broken 
up into granules. They constitute, together with a mixture of food 
particles, the formed elements that are to be seen circulating in 
the living animal and whirling about in eddies at the bases of the 
dorsal tentacles. In appearance they are strongly suggestive of ova. 
Cell division may be continued, after the cells are budded off. 
The morphology of the digestive cells lining the alimentary 
tract in insects has been described by many observers, — notably 
NEEDHAM 1897, VAN GEHUCHTEN 1890, and Baupranr 1890, — and 
the similarity to the conditions in Coeloplana is striking. Like- 
weise in a hydroid, Corymorpha, May 1903 has described a process 
very similar to what takes place in Coeloplana. In the former cases 
the cells become “loaded” with densely staining secretion and break 
off or extrude portions into the digestive cavity. In Coeloplana, in 
contrast to the conditions in insects, the endothelial tissue is homo- 
geneous, there is no central “nidus” and the contents of the budded 
off cells does not stain differently from the parent tissue. The cyto- 
plasm never has the appearance of being sloughed off or squeezed 
out, such as seems to be the rule in Corymorpha and insects. The 
floating bodies in Coeloplana are cells arising by direct proliferation 
from the epithelium. 
Of especial interest in the development, in Coeloplana, of typical 
