68 



ZOOLOGY 



SECT. 



CLASS II.-MYCETOZOA. 



1. EXAMPLE OF THE CLASS Didymium difforme. 



Didymium occurs as a whitish or yellow sheet of protoplasm (Fig. 51, G) 

 eften several centimetres across, which crawls, like a gigantic Amoeba, over 

 the surface of decaying leaves. It shows the characteristic streaming move- 



PIG. 51. Didymium difforme. .4, two sporangia (spg. 1 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 (nu.). D, the same after loss 

 of flagellum ; b, an ingested Bacillus. E, an amoebula. F, conjugation of amo?bulae to 

 form a small plasmodium. O, a larger plasmodium accompanied by numerous amoebulo* ; 

 sp. ingested spores. (After Lister.) 



meats of protoplasm, and feeds by ingesting various organic bodies, notably 

 the Bacilli which always occur in great numbers in decaying substances. 

 Numerous nuclei are present. Certain of these become differentiated as 

 sexual nuclei which throw off a portion of their substance and coalesce in pairs. 

 After leading an active existence for a longer or shorter time, the proto- 

 plasm aggregates into a solid lump, surrounds itself with a cyst, and undergoes 

 multiple fission, dividing into an immense number of minute spores. The 

 cyst (Fig. 51, A, sjxj. 1, spy. 2) is therefore not a mere resting capsule, like that 



