THE XEMATOCYSTS OF EOLIDS 
129 
times, branch connections to other cells. Though visible onl}^ in 
sections, the projections suggest activity, as if they had been fixed 
in the act of moving, or flowing. It is interesting that cnidophores 
well-stocked, do not contain these labyrinths. Apparently if 
the ''fishing" results in a ''catch," the cells withdraw their pseu- 
dopods. 
Not all the cells produced by the embryonic zone become cnido- 
phages. In addition to these, certain interstitial cells are formed 
Fig. 7 Transverse section through a ceras in which the lumen is made labyrin- 
thine by pseudopodia that project inwards from the bounding cnidophages. Drawn 
by Mr. Carl Kellner. 
whose fate is quite different. Fig. 8 illustrates part of a longitu- 
dinal section through basal cnidophages. The cells have ingested 
no nematocysts, but those which were about to, differ distinctly 
from the prospective interstitial cells. The latter are very narrow, 
have near their bases small densely staining undifferentiated 
nuclei, and have cytoplasm, which, wherever visible, resembles 
that found in the embryonic cells. Near the lumen of the cnido- 
phore the interstitial cells have no membranous boundaries, 
although elsewhere they are definitel}^ delimited. 
THE JOURNAL OF EXPERIMEXTAI ZOOLOGY, VOL. 9, XO. 1. 
