A Monograph of the Myxogastres. 5 



importance to place the Mycetozoa outside the vegetable 

 kingdom, the formation of a plasmodium in the Myxomycetes, or 

 the aggregation of swarm-cells in the Acrasieae, the two primary 

 divisions of the Mycetozoa, it is necessary to commence with 

 the germination of the spore. In the Myxomycetes, the spores 

 on germination give origin to one, two, or more naked cells, 

 which possess the power of movement due to the protrusion of 

 pseudopodia or the presence of a cilium ; these cells are known 

 as swarm-cells. The swarm-cells possess a nucleus, multiply by 

 bipartition, and eventually coalesce to form a plasmodium in 

 the following manner. After the production of numerous 

 swarm-spores by repeated bipartition, little groups are formed 

 by the close approach of two or more of these bodies; these 

 groups often disperse again, but eventually the components of 

 a group coalesce, and lose their individuality ; this coalescence 

 and loss of individuality results in the formation of a small 

 plasmodium, which, in some unknown way, possesses the power 

 of attracting surrounding free swarm-cells ; these at once coalesce 

 and add to the bulk of the plasmodium. The nuclei of the 

 component swarm-cells retain their individuality in the plas- 

 modium, the latter retaining the power of motion originally 

 possessed by its components, and represents the vegetative 

 phase of a Myxogaster. The above is De Bary's conception of 

 the formation of a plasmodium, to which may be added, in his 

 own words " Nuclei were not at first observed in the plasmodia. 

 Cienkowski even stated expressly that the nuclei present in 

 the swarm-cells disappear when they coalesce. But Schmitz 

 and Strasburger have recently established the presence of 

 numerous nuclei in the plasmodium, and it may be presumed 

 that they are the persistent nuclei of the swarm-cells and 

 products of their division." * The presence of a thick, colourless 

 membrane surrounding the plasmodia in Lycogala, Arcyria 

 punicea, and Stemonitis fusca has been noted by De Bary, who 

 also found that in the last-named species, the inner and thicker 

 portion of the envelope became blue with iodine. Under 

 certain conditions unfavourable for active vegetative work> 



1 Tom. cit. p. 425. 



