COE: TERRESTRIAL NEMERTEAN OF BERMUDA. 561 
somewhat crescentic in transverse section (pi. 25, fig. 18), the horns 
of the crescent extending laterally and dorsally into the region later 
occupied by the intestinal lobes. 
The exact relation of the endodermic cells to the cells which 
later form the lining of the intestine is difficult to determine. 
Lebedinsky (’ 97 ) describes the delamination by which the lumen of 
the intestine is formed in the solid mass of endoderm cells in 
Tetrastemma and Drepanophorus. As in Geonemertes, the intes¬ 
tinal lumen is here surrounded by several layers of vacuolated 
endodermic cells. Of these the cells immediately lining the lumen 
very soon become columnar in shape and, together with a portion or 
all of the more peripheral cells, form the columnar epithelium of the 
intestine in the adult. In any of these cases it is impossible to deter¬ 
mine whether all the cells of the original endoderm are later pre¬ 
served in the intestinal epithelium or whether the central cells form 
this epithelium and absorb the cells situated more peripherally. 
At this time, when the intestinal cells are being rearranged by the 
ingrowth of the fibrous dissepiments to form the intestinal lobes, 
the cells become very much vacuolated and the cell boundaries very 
indistinct. It is certain that the intestinal epithelium is derived 
from the mass of the endodermic cells, but whether all or only a 
portion of these cells preserve their individuality in the adult intes¬ 
tine is undetermined. 
The intestinal lumen becomes a broad canal which remains for 
some time without indication of lobes, very much as in the adult 
body of some of the Paleonemertea, but at a later period vertical 
fibrous dissepiments grow in, uniting the dorsal body walls with the 
ventral and dividing up the lateral portions of the intestinal canal 
into shallow pouches. The position of these dissepiments does not 
seem to be marked out previous to their formation, either in the 
intestinal epithelium or in the body walls. They are first indicated 
as slightly thickened strands of connective tissue, which divide the 
endodermic cells into groups at regular intervals. As a rule they 
are about as widely separated as the width of two to four endo¬ 
dermic cells, so that in a parasagittal section of the body at this 
stage the endodermic cells are seen to be divided into vertical 
groups perhaps five to ten cells high and two, three, or four cells 
wide (pi. 24, figs. 14, 15). The groups of cells are arranged in 
regular pairs, each group corresponding to a future intestinal lobe. 
