446 BIOLOGY OF THE PROTOZOA 



The zygotes thus formed are very miscible and fusion occurs when 

 two or more come in contact. In this way, and by multiplication 

 of the nuclei by mitosis, and growth, great multinucleated plasmodia 

 arise which may grow to be many inches in diameter and with 

 thousands of nuclei. All observers agree in describing the fascinat- 

 ing spectacle of these sheets of moving protoplasm, a phantas- 

 magoria of living and lifeless granules, nuclei, foreign particles 

 and pigment. The pseudopodia are myxopodia and by their anas- 

 tomosis great networks of flowing protoplasm form traps for minute 

 organisms utilized as food ; some forms, in addition, may be saprozoic 

 in nutrition. 



Under conditions which are not entirely known, but some of 

 which are drought and scarcity of food, the entire mass may pass 

 into a resting condition. The fluid protoplasm hardens to form a 

 thick-walled "sclerotium" which is frequently impregnated with 

 calcium salts. The nuclei collect in groups and these become 

 encysted with cellulose walls. Such resting forms may retain life 

 for some years. Ultimately the hardened walls are liquefied and 

 the plasmodium condition is regained, the process requiring hours 

 or days according to the length of time in the dried state. 



With maturity of the plasmodium the gametes, or gametocytes, 

 are formed by processes which are quite remarkable for their intri- 

 cacy and for the complexity of the specialized structures appearing 

 only at the time of fructification. The whole plasmodium may form 

 one "sporangium," but more often the plasmodium breaks up into 

 several "spore "-forming groups or "sporophores," each from a local 

 heaping of the substance of the plasmodium. Part of such a thick- 

 ening forms an outer investing wall termed the peridium which is 

 often further hardened by deposition of lime. Another portion 

 becomes differentiated into a thick network or feltwork, termed the 

 capillitium, which is continuous with the outer peridium (Fig. 184). 

 This network is made up of tubes and fibers; some of the latter, 

 termed elaters, have a spiral structure and are supposed to function 

 in the distribution of the spores. According to Kranzlin elaters 

 arise from the kinetic components of degenerating nuclei. 



The formation of the spores varies in details but the essential 

 part of the process is the fragmentation of the residual mass into 

 uninucleate or multinucleate bits of protoplasm. If multinucleate 

 further fragmentation results in uninucleate bits, each of which 

 encysts independently. According to the later observations of 

 Jahn, the supposed fusion of nuclei leading to the uninucleate con- 

 dition, and interpreted as autogamic fertilization by Prowazek, 

 Kranzlin and earlier, by himself, is only a phase in the degeneration 

 of nuclei many of which are disposed of in this way at this period. 

 Fertilization is exogamic, the gametes being the myxamebae and 

 myxoflagellates which ultimately emerge from the spores. 



