6 THE LOWER FUNGI— PHYCOMYCETES 



include them in the Protozoa. In some modern classifications 

 no attempt is made to maintain a definite line of separation 

 between the plant and animal kingdoms at their lower levels. 

 Instead the group Protista is used to include the primitive 

 forms of life which lie on the borderline. This is indicative 

 of the general state of uncertainty concerning the interrelation- 

 ships of these various simple forms, but should not be 

 assumed to have resulted from ignorance of the various individual 

 groups. 



Myxomycetes. — Knowledge of the taxonomy of the Myxomy- 

 cetes (Mycetozoa, shme moulds) has reached a high plane, the 

 group having been long known and critically studied. The 

 monographic treatises of Lister (1925) and Macbride (1922) are 

 excellent and comprehensive. Moreover, investigations by 

 Jahn (1907, 1908, 1911), Harper (1900, 1914), Harper and 

 Dodge (1914), Strasburger (1884), Bisby (1914), Olive (1907), 

 Skupienski (1918, 1927, 1928), Gilbert (1927, 1928 a, h, c), 

 Elliott (1916), Sanderson (1922), and others on the morphology, 

 life history, and nuclear phenomena in these forms have given 

 us a resonably intimate knowledge of the group. 



The Myxomycetes correspond with the Acrasieae and Labyrin- 

 thuleae in that in all three, a vegetative, phase, in which the 

 organism moves and feeds, alternates with a fruiting phase in 

 which it is quiescent. The Myxomycetes in the fruiting phase 

 form definite spores, the walls of which have been found in some 

 genera at least to be composed of cellulose. In germination the 

 spore frees one or more naked uninucleate protoplasts. The num- 

 ber is usually one, but in several species (Gilbert, 1928 6 : 350) is 

 variable (1-4), and in Ceratiomyxa is said to be eight. These 

 protoplasts emerge as swarmspores. Though naked, and to a 

 degree amoeboid, especially at the posterior end, they are provided 

 with a cilium (flagellum) at the anterior end which lashes about 

 and gives the cell a peculiar, whirling, dancing motion. In a few 

 cases cells are found to be provided with a pair of cilia at the 

 forward end (Gilbert 1927). After swimming for a time as 

 swarmspores the cells usually lose their cilia and crawl about 

 by amoeboid movements. They are then termed myxamoebae. 

 Both in the ciliate and amoeboid states the cell is capable of 

 ingesting solid food (Gilbert 1928 a, c), and in either state a 

 temporary encystment of the individual to form a microcyst 

 may result from drying out in an unfavorable environment. 



