52 PROTOMYXA AND THE MVCETOZOA 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 amoebulae 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 of a single amcebula 

 but by the conjugation or fusion of a variable number of 

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

 amcebulae is called a plasmodiuiu, 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 

 short consideration of the strange group of organisms known 

 as Mycetozoa or sometimes " slime-fungi." They occur 

 as gelatinous masses on the bark of trees, 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^ 

 Chondrioderma, &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. (ift.) in diameter, 

 and throughout the substance of which are found numerous 

 nuclei. In this condition they creep about over bark or some 



