THE MYCETOZOA 



43 



swimming flagellate zoospore, the flagellum is permanently with- 

 drawn and the organism passes into the amoeboid stage, which, as we 

 have seen, may be temporarily assumed daring the flagellate period. 

 They now creep about, adherent to other objects, emitting blunt 

 pseudopodia, and in this as in the preceding stage they may pass 

 into the condition of microcysts. 



Each individual in the amoeboid phase of the life-history is the 

 lineal descendant, through the successive divisions of the flagellulate 

 phase, of a particular spore ; but from 

 the amoeboid phase onward the in- 

 dividuality is lost. This results from 

 the remarkable process, first seen by 

 Cienkowsld (7), of fusion of the 

 amoebulae to form plasmodia. The 

 amoebulae present in a particular area 

 draw together into groups, becoming 

 endowed, apparently, with the power 

 of mutual attraction, and the groups, 

 once formed, act as centres to which 

 neighbouring amoebulae, scattered 

 through the water, converge. After 

 coming in contact with one another 

 they remain at first visibly distinct, 

 but after a short time a complete 



fusion of the protoplasm occurs. In this manner, the amoebulae 

 from all sides falling in and fusing in the common mass, the 

 plasmodia are produced. 



(c) The Plasmodium. 



The name plasmodium was first applied by Cienkowski in 1862 

 (6, p. 326) to the large expansions of protoplasm which form the 

 dominant phase of the life-history of the Euplasmodida. On his 

 subsequent discovery (7), in 1863, of their mode of origin by the 

 fusion of amoeboid swarm-cells, Cienkowski stated (p. 421) that such 

 a mode of origin must be included in the definition of a plasmodium. 



The question arises whether, in this fusion of amoebulae to form 

 the plasmodia, we have a phenomenon comparable with the conjuga- 

 tion of the gametes of other forms, a view to which the mutual 

 attractiveness with which the amoebulae become endowed appears 

 to offer some support. If the analogy were complete, we should 

 expect that a fusion of nuclei would occur as well as a fusion of the 

 protoplasm of the amoebulae. But the evidence which we have at 

 present as to the behaviour of the nuclei lends no support to this 

 view. As many as eight amoebulae have been watched successively 

 fusing into a common mass, and their eight nuclei have been seen, 

 distinct, in the young plasmodium thus formed (18, p. 5). When 



Fio. 5. 



Amoebulae of Dulymium di/ormc 

 uniting to form a plasmodium. a, 

 separate amoebulae ; m, microcysts ; 

 pi, young plasmodium with ingested 

 bodies, x about 320. (After A. Lister, 

 18.) 



