153 
The cells of the celomic epithelium and the ecelomic 
corpuscles perform excretory functions; carmine granules 
injected into the ccelom are taken up by these cells and by 
the nephridia (see G. Schneider, Zeitschrift fiir Wiss. 
Zoologie, Band 66, pp. 505-507, 1899). Chlorogogen 
granules are present in many of the cells of the coelomic 
epithelium. 
A great proportion of the reproductive cells present 
in the coelomic fluid, instead of floating freely, accumulates 
in the space between the oblique muscles and the ventral 
body wall. In females oocytes in various stages of growth 
and varying in diameter from ‘02—16 mm. may be seen. 
In males various stages in the development of spermatozoa 
from groups of young spermatogonia, consisting of about 
eight cells to the masses of spermatids seen in Fig. 65, 
may be found. 
The celomic fluid is kept in motion by contractions 
of the body wall. In a specimen freshly taken from the 
sand one usually observes a series of peristaltic waves 
arising in the posterior part of the gill region, and 
running forwards to the anterior end, producing a pro- 
gressive swelling of the body, due to the carrying forward 
of the cceelomic fiuid, which, as soon as the wave is past, 
flows backwards again. This motion is of considerable 
importance in promoting the efficient circulation of the 
celomic fluid, in inflating the anterior portion of the 
animal, thus aiding in burrowing, in assisting the com- 
paratively weak gut muscles to cause the backward motion 
of the sand in the alimentary canal, and, when the animal 
is in its burrow, in providing frequent changes, practically 
a current, of sea-water to bathe the external surface and 
the gills. 
