52 PROTOMYXA AND THE MYCETOZOA LESS. 



proof of the statement made in a previous Lesson (p. 34) 

 that a flagellum is nothing more than a delicate and rela- 

 tively permanent pseudopod. In Protomyxa we have a 

 flagellula directly converted into an amcebula, the flagellum 

 of the former becoming one of the pseudopods of the 

 latter. 



The amcebulae thus formed may simply increase in size 

 and send out numerous delicate pseudopods, thus becoming 

 converted into the ordinary Protomyxa-form. Frequently, 

 however, they attain this form by a very curious process : 

 they come together in twos and threes until they are in 

 actual contact with one another, when they undergo complete 

 and permanent fusion (G). In this case the Protomyxa-form 

 is produced not by the development ot a single amcebula 

 but by the complete fusion of a variable number of 

 amcebulae. A body formed in this way by the fusion of 

 amcebulae is called a pla smodiiim, so that in the life-history 

 of Protomyxa we can distinguish an encysted, a ciliated or 

 flagellate, an amoeboid, and a plasmodial phase. 



The nature of a plasmodium will be made clearer by a 

 brief general consideration of the strange group of organisms 

 known as Mycetozoa or sometimes " slime-fungi," to which 

 Protomyxa itself very probably belongs. The best known 

 members of the group occur as gelatinous masses on the 

 bark of trees, on dead leaves, on the surface of tan-pits, and 

 sometimes in water. It must be remembered that Mycetozoa 

 is the name not of a genus, but of a class in which are 

 included several genera, such as Badhamia, Physarum, c. 

 (see Fig. 7) : a general account of the class is all that is 

 necessary for our present purpose. 



The Mycetozoa consists of sheets or networks of proto- 

 plasm which may be as much as 30 cm (i ft.) in diameter, 



