58 
ORGANIC DEPENDENCE AND DISEASE 
Figs. 44, 45. Sponges from the English Chalk showing spiral annelid tubes. In 
both the worm is seen to encircle the cloaca of the sponge and at some distance 
from it (Fig. 44, section). In Fig. 45 the direction of the spiral is the reverse 
of that in Fig. 43. From Beckhampton. (Courtesy of Dr. F. A. Bather.) 
Symbiosis in the worms and crinoids. The data for such 
association are not abundant. Myzostomum, a wormlike 
creature, believed to be an annelid, is parasitic on living 
crinoids where its species cause galls or SAvellings by the 
overgrowth of the calcareous substance. On the columns of 
Paleozoic crinoids small gall-like protuberances are occa- 
sionally found, with a central perforation, and several 
authors have ascribed these to the Myzostomum . 1 These 
Myzostomid galls (Myzostomites) have been recorded from 
rocks as early as the Upper Ordovician, but we must confess 
to knowing very little about them, and some of the pit- 
tings and depressions on crinoid columns which have been 
thought to be the inner cavities of Myzostomid cysts are 
doubtless of other origin. Perhaps the best proof that these 
galls have been made by infesting worms is afforded by the 
i See Waclismuth and Springer. 1897, p. 43, pi. 1, fig. 2; p. 502, pi. 39, 
fig. 7; R. L. Moodie; F. A. Bather. 
