14 



INTRODUCTION 



dowed with amoeboid movements, — creeping movements char- 

 acteristic of the genus Amoeba, to be described in the next 

 chapter ; this structure is called a plasmodium, and its color 

 varies in different species, being often whitish or yellowish. 

 They feed largely on bacteria, which are minute unicellular 

 plants occurring in great abundance in decaying organic matter. 



FIG. i. Didymium difforme. A, two sporangia | tpg, i and 2) on a fragment of leaf (/) ; 



B, section of sporangium, with ruptured outer layer (a), and threads of capillitium (cp) ; 



C, a flagellula with contractile vacuole (c. vac) and nucleus (««) ; D, the same after loss 

 of flagellum ; b, an ingested bacillus; E, an amcebula; F, conjugation of amcebula 

 form a small plasmodium ; G, a larger Plasmodium accompanied bv numerous amcebula-; 

 sp, ingested spores. (After Lister, from Parker and Haswell's Text-book.) 



After a time portions of the protoplasm of the plasmodium 

 assume more definite shapes and secrete firm membranes about 

 themselves, thus forming closed capsules or cysts, which may 

 be spherical, ovoid, or considerably elongated, and in some cases 



