10 Prof. A. G. Bourne. On a Hydroid Phase of [Dec. 11, 



The Hydroid Form. 



I discovered upon some of the root filaments of the plants of 

 Pontederia which were growing in the tank in great profusion, an 

 organism, which in its method of growth somewhat resembles an 

 encrusting sponge. It occurs very abundantly upon some of the 

 roots, and is not to be found upon others. I am unfortunately unable 

 to say whether the roots upon which it occurs were near together 

 or scattered through the tank. I have not seen it upon any young 

 roots, while on the other hand it is most abundant upon the oldest 

 and blackest roots. Where most abundant there are four or five- 



Tig. 1. Hydroid forms of Limnocodium Sowerbii. 

 E. Koot filament of Pontederia; A, B, C. Colonies of various sizes; D. Portion- 

 of a Hydroid in optical section, slightly diagrammatic ; JEct. Ectoderm ; End„ 

 Endoderm; m. "mouth;" nem. Nematocysts ; p. Perisarcal tube of adventitious- 

 particles. 



