232 The Sarcodina 



haps by contractions induced by desiccation, probably helps to distribute 

 the spores after rupture of the peridium. During development of the 

 capillitium, nuclear division may continue in the sporangial protoplasm 

 for a time, but uninucleate pre-spores eventually are produced. These 

 become enclosed in membranes to form the characteristic spores. 



In addition to sporulation, another method of producing resistant 

 stages is known in the Eumycetozoina. An entire plasmodium may be- 



Fig. 5. 22. A-I. Physariim polycephalum, xl360 (after Howard): A. Spore. 

 B. Completion of mitosis; spore membrane ruptured. C. Completion of fission 

 at excystment. D. Amoeboid flagellate. E. Swimming flagellate. F. Flagellate 

 zygote shortly after fusion of gametes. G. Amoeboid zygote after loss of 

 flagella. H. Encysted zygote; gametic nuclei not yet fused. I. Zygote after first 

 nuclear division in formation of young plasmodium. J-L. Arcyria cinerea 

 (after Kranzlin): J-K. Stages in development of sporangiimi, x23. L. Portion 

 of cross-section through a sporangium, showing spores, peridituii, and part 

 of a capillitial thread ("elater"), x375. 



come sclerotized (17) upon subjection to desiccation. The plasmodium 

 becomes partly dehydrated and is enclosed in a membrane, the sclerotiuni, 

 said to consist inainly of cellulose. Once sclerotized, the organism can re- 

 main viable for several months and then become active again in the 

 presence of adequate moisture and oxygen. 



Development of the spores after liberation seems to be a complicated 

 process. Prior to germination, each spore in Ceratiomyxa (41) develops 

 four nuclei, so that a quadrinucleate amoeboid stage is released. The 

 amoeboid stage is said to produce eight uninucleate myxoflagellates, sup- 



