6o 



THE MYCETOZOA 



liminary step to sporulation, the amoebulae draw towards their 

 fellows in groups, which may be composed of many hundreds of 

 units, but they maintain their individual distinctness and do not 

 fuse to form a true plasmodium as in the Euplasmodida. Spore- 

 production occurs in air, at the surface of the substance in which 

 the vegetative phase has been spent. 



In Guttulina, as well as in the members of the Dictyosteliaceae, a 

 remarkable differentiation occurs among the amoebulae forming the 

 pseudoplasmodium, comparable with that characteristic of the 



organisation of the Metazoa. 

 Some of the amoebulae secrete a 

 firm membrane and become joined 

 end to end to form a stalk (Fig. 

 1 9, c and d), attached below to the 

 substratum, and up this the other 

 amoebulae climb and pass into the 

 encysted condition at the top as 

 a naked cluster of spores. In 

 Didyostelium the stalk is long and 

 simple ; in Folysphondylium it is 

 branched (Fig. 19, d). 



Tlie supporting structures of 

 the Sorophora are evidently of a 

 different nature from those of the 

 Euplasmodida, in which they are 

 not cellular, but formed as secre- 

 tions of the protoplasm. 



It is, of course, possible that 

 the pseudoplasmodia of the Soro- 

 phora may represent a stage in 

 the evolution of the true plas- 

 modium, which in the other group 

 is such an important phase of the 

 life -cycle; but it appears more 

 probable that both Euplasmodida 

 and the Sorophora are to be 

 derived from some simple forms 

 with a life-history resembling that 

 of Protomonas or Bursulla among 

 the Proteomyxa. 



Fio. 19. 



a and 6, Copromyxa protea, Fayod. a, a 

 simple, b, a branched form of sorus, slightly 

 magnified (after Fayod. ) c and d, Poly- 

 sphondylium violaceurn, Brefeld. c, a young 

 sorus, seen in optical section, with a mass 

 of amoebae grouped round the stalk, and 

 others still extended about the base, x 110. 

 d, a sorus approaching maturity. The stalk 

 has become compound. The lowest whorl 

 of secondary sori is complete, those above it 

 are in varying degrees of completeness, x 20. 

 (After Brefeld. From Zopf, 24.) 



Two hundred and sixty -five 

 species of the Euplasmodida are 

 described in the British Museum Catalogue (18); Zopf (24) 

 enumerated nine species of Sorophora, and Olive (20), more 

 recently, twenty. 



