60 CASPER 0. MILLER. 



Plasmodia increase* iu number and in size, but they are not seen 

 macroscopically. If the culture be one which forms sporangia 

 on the thirtieth day^ and it is examined about the twenty-sixth 

 day, one finds more small plasmodia and a smaller number of 

 microcysts present in the fluid than at the previous examina- 

 tions, A large plasmodium appears, rather suddenly, on the 

 twenty-eighth day, lying on the hay at the surface of the fluid. 

 It does not increase noticeably iu size for two days, and then 

 passes up the side of the flask to form sporangia. If the fluid 

 is examined the small plasmodia have disappeared for the most 

 part from the fluid. 



One may have examined the culture the previous day without 

 having macroscopically observed the presence of a plasmodium. 

 It must have originated by the fusion of a number of small 

 plasmodia, or have grown as a large plasmodium in the interior 

 of the stalks of liay. One stalk of hay is not large enough to 

 accommodate the plasmodium, and no branches of plasmodia 

 are seen connecting the various stalks. The writer is of 

 the opinion that it originated by the fusion of a number 

 of small plasmodia. Plasmodia large enough to be seen macro- 

 scopically have been observed by the writer to fuse on the 

 slide. 



What takes place in the culture seems to be as follows : — 

 the bacteria multiply at the expense of a portion of the nutrient 

 material : the zoospores multiply at the expense of the bacteria, 

 and possibly some nutrient material which was not consumed 

 by the bacteria; the majority of the zoospores encyst; small 

 plasmodia develop from a single zoospore or by the fusion of 

 several zoopores ; the plasmodia take in and digest active 

 and excysted zoospores and bacteria; finally, the small plas- 

 modia fuse to form the large plasmodium. 



Celakovski (38) studied the action of the plasmodia Chond. 

 diff., Didymium microcarpon, and /Ethalium septicum 

 on various substances placed in the fluid with them. He saw 

 them take in microcysts which, after ingestion, were not found 

 in vacuoles, but were simply surrounded by protoplasm. After 

 two days the microcysts were expelled unchanged ; if dried 



