Tilclen: pilinia and stigeoclonium. 619 



mainder of the inner surface of the vessel was tinged with dull 

 green, which was caused by the presence of the plant in the 

 Palmella stage to be hereafter described. 



This behavior of the zoospores suggested a plan for sowing 

 them for the purpose of studying their germination. By the 

 following method an almost pure culture of the Pilinia or 

 Stigeoclonium spores was obtainable: 



A small beaker, painted black with the exception of a space 

 about an inch square on one side near the top, was filled with 

 water. In this was suspended a hanging drop cell in such a 

 way that its cover-glass fitted over the unpainted square and 

 presented its under surface to the water. The water covered 

 a portion of the glass. Zoospore-forming material, taken from 

 the pebble at about 10 a. m. when the zoospores were in the 

 most active motion, was placed on the lower ledge of the 

 suspended cell with the expectation that the zoospores in seek- 

 ing the light would come to rest upon the under side of the 

 cover- glass at the surface of the water. This they invariably 

 did, losing their cilia in a few hours and becoming attached to 

 the glass most satisfactorily. The convenience of this 

 arrangement is apparent. The cell could now be removed 

 from the beaker and placed under the microscope for examina- 

 tion, and returned at pleasure to the beaker or to a moist 

 chamber. If kept in the moist chamber the drop of water may 

 be drawn off and a fresh one added at intervals, without the 

 least danger of displacing or injuring the germinating spores. 

 This cannot be done when the spores have been removed from 

 the sides of the tank and placed in a cell for they will not at- 

 tach themselves a second time. With the method described, if 

 it were necessary to watch a certain group of spores during a 

 period of several days, a circle was drawn with ink on the top 

 of the cell coverglass within which were the individuals to be 

 studied, and thus they were easily found with the low power 

 of the microscope. Otherwise when the spores are at all 

 numerous in the mount, it is often difficult to find the same 

 ones a second time. 



Several hours after the spores had ceased swarming for the 

 day, the hanging cell was removed from the tank and ex- 

 amined. A large number of spores had collected on it at the 

 level of the water. They were quite varied in size and form 

 and each contained an eye-spot near the anterior end and some 

 granules (PI. XXXIV, fig. 7). The spore is evidently caused to 



