EPITHELIOID MEMBRANES IX MOXAXONID SPOXGES 557 
Hal lining contracts, we may suppose, after the fashion of a sphinc- 
ter, locally or throughout the extent of the pore canal, and so 
tends to obliterate the lumen. Such contraction brings with it 
a centripetal streaming of the mesenchyme of the dermal mem- 
brane. The closure of the canal is certain!}' not brought about 
by the contraction of surrounding fibre-like cells arranged in 
sphincter fashion. There are none of these. 
In the centripetal streaming of the dern^al mesenchyme we 
must distinguish active movements of cells and passive movements 
of intercellular jell}-. Both undoubtedly occur. On the active 
movements of such cells I may record the following few observa- 
tions. The conspicuous cells in the mesenchyme of the dermal 
membrane are coarsely granular amoebocytes (cells a, c, in fig. 
13) and pale cells either without coarse granules or with only 
a few (cells d, b, in fig. 13). Both varieties of cells may appear in 
the spheroidal shape. When they are actively moving they are 
irregular in shape, the body extending out into slender prolon- 
gations. Cells of both varieties contantly shift their position, 
and undergo changes of form, all very slowly. The granular 
amoebocytes move more actively than the pale cells. The cells 
a, and c crossed the space included between the spicules, passing 
over b which they obscured for a time. In crossing the space, cell 
a consumed five minutes. 
CLOSURE OF PORES IN LISSODENDORYX 
The species used was LissodendorjTc carolinensis, a common 
form in Beaufort harbor, and a description of which is contained 
in a paper now in press for the U. S. Bureau of Fisheries. The 
sponge falls in the halichondrine monaxonida. The whole sur- 
face is abundantly covered with tubular translucent papillae the 
walls of which are perforated with numerous pores. These pore- 
papillse which are often slightly branched are contractile and 
may almost entirel}^ disappear. When dilated they are about 
3-5 mm. long and 1 mm. in diameter. 
If such pore-papillae in the expanded state are cut off and 
mounted in sea water, many pores are found to be open, and their 
