40 ORGANIC DEPENDENCE AND DISEASE 



tooned and wavy markings in the sand, made by the occu- 

 pants of these tubes as they swept the sea bottom with their 

 extended bodies. They were eager commensals and in the 

 Paleozoic faunas we find them in various associations, espe- 



Fig. 1. Silicified mass of stromatoporoid coi*al full of straight worm tubes (Gitonia) 

 which start at various levels in the coral growth. Onoudaga limestone (Lower 

 Devonian). 



Fig. 2. A solid colony of Stromatopora conslellata from the Upper Silurian (Coble- 

 skill limestone) with its surface pitted by the openings of vertical tubes of the worm 

 Gitonia sipJio. 



