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 swellings 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 Wachsmuth and Springer. 1897, p. 43, pi. 1, fig. 2 ; p. 502, pi. 39, 

 fig. 7; E, L. Hoodie; F. A. Bather. 



