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 



F IG . 98. _ Flagellula of differentiated in any way. The plasmodia 



Stemonitis fusca, show- are often brightly coloured. 

 ins successive stages in ^ ,, . , ,. ,. r ,, , ,. 



the capture of a bacillus. From tlieir mocle of llfe > tlie plasmodia 



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



a? e the f htSTin 1 : *is occurs the plasmodium passes into the 

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



a 



an 



anterior vacuole. 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 



protoplasmic body, and 



takes the form of a 



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



attachment known as the hypothallus. Between the sporangium 



: ? 



a plasmodium of Badhamia 

 utricularis expanded over a slide. From 

 Lister, magnified 8 diameters. 



