MYCETOZOA. 133 



which grow on the bark of old stumps. An example of the latter 

 character was exhibited under a bell jar to the members of the 

 Club. It extended over several inches of surface, in a close network 

 of veins with a turgid advancing border. Through this nejbwork, 

 as was seen under the microscope, the substance of the plasmodium 

 streams in a rhythmic flow of circulation ; this flow continues for 

 about a minute and a-half in one direction, it then comes to a 

 stand, and immediately the current is reversed and is continued for 

 about the same length of time in the opposite course, but for a 

 somewhat longer period in the diiection in which the plasmodium 

 is advancing like waves in a rising tide. 



After remaining in this form for a period of weeks or months, 

 or in some species for a year, the plasmodium throws itself into 

 the graceful shapes and varied structure characteristic of the final 

 stages of the different genera ; in a short time the spores are formed, 

 and the cycle of changes is completed. 



De Bary thought that the swarm cells derived their nourishment 

 solely by the absorption of nutrient matter in solution, but it is 

 now found that to a large extent at least they feed on bacteria. 

 The creature projects pseudopodia from the posterior end of the 

 body, to which, as it swims, bacteria become attached and are 

 drawn in and surrounded by a digestive vacuole. I have watched 

 a swarm cell catch three bacilli and convey them to the same 

 vacuole, and in the course of an hour and a-half the bacilli have 

 been gradually dissolved until not a trace of them remained and 

 the vacuole became merged in the granular protoplasmic substance. 

 When a large bacillus is caught a tube-like extension of the body 

 material is often projected, investing the captive, which is sucked 

 in, and in a short time a vacuole is formed round it. On one 

 occasion I had a host of swarm-cells of Stemonitis fusca under the 

 microscope which had hatched in about half-an-hour after having 

 been wetted : to these I supplied a drop of water teeming 

 with active bacilli ; two swarm-cells caught hold of a bacillus 

 about five micromillimetres in length at the opposite ends, for 

 20 minutes they struggled which should obtain possession of 



