240 



THE PROTOZOA 



be several inches across and contain many thousands of nuclei. 



The plasmodium moves about in various directions, showing 

 exquisite streaming movements of the proto- 

 plasmic body (Fig. 99). The nature of the 

 food varies in different species ; the majority 

 feed on dead vegetable matter, but some 

 attack and devour living fungi. The mode 

 of nutrition is generally holozoic, but in 

 some cases perhaps saprophytic. Contractile 

 vacuoles are present in large numbers in 

 the protoplasm, in addition to the innumer- 

 able nuclei, which are all similar and not 



FIG. 98. Flagellula of differentiated in any way. The plasmodia 

 Stemonitia fusca, show- are often brightly coloured. 



From their mode of life, the plasmodia 



ing successive stages in 

 the capture of a b&cillus. 



an anterior vacuole. 



In a it is captured by are naturally liable to desiccation, and when 

 aTthl htdHndTin * *his occurs the plasmodium passes into the 

 it is enclosed in a diges- sclerotial condition, in which the proto- 

 plasm breaks up into numerous cysts, each 

 containing ten to twenty nuclei. When 

 From Lister, magnified mo istened, the cysts germinate, the con- 

 tained masses of protoplasm fuse together, 

 and so reconstitute the active plasmodium again. 



The plasmodium represents the trophic, vegetative phase, which 

 is succeeded by the reproductive phase, apparently in response to 

 external conditions, such 

 as drought, but more es- 

 pecially scarcity of food. 

 The reproduction begins 

 by the plasmodium be- 

 coming concentrated at 

 one or more spots, where 

 the protoplasm aggre- 

 gates and grows up 

 into a lobe or eminence, 

 the beginning of the 

 sporangium (Fig. 100), 

 the capsule in which the 

 spores are found. The 

 sporangium is modelled, 



as it were, on the soft FlQ - " Part of * , pfcwnodium of Badhamia 

 . . ' vtricularis expanded over a slide. Irom 



protoplasmic body, and Lister, magnified 8 diameters. 



takes the form of a 



rounded capsule, attached to the substratum by a disc-like 



attachment known as the hypothallus. Between the sporangium 



