I 6 MYCOLOGY 



.flagellum at the anterior end and creep in a linear form with the flagellum 

 extended in advance, or swim about in the water with a dancing move- 

 ment occasioned by the lashing of the flagellum. They have a single 

 nucleus and a contractile vacuole. To a large extent they feed on 

 bacteria which are swallowed by pseudopodia which project from the 

 posterior end of the cell. The swarm cells increase rapidly by biparti- 

 tion. When this takes place, the flagellum is first withdrawn and the 

 main cell assumes a globular form; it then elongates and a constriction 

 occurs at right angles to the long axis. The nucleus divides by karyo- 

 kinesis and in the course of a few minutes the halves of the nuclear 

 plate separate and retreat to the opposite ends of the constricted cell 

 which now divides into two, each new cell acquiring a flagellum. 

 Sometimes the swarm cells become encysted to form the so-called 

 microcysts, or zoocysts. 



The spores of Ceratiomyxa, which are borne on the outside of 

 column-like sporophores, are white in color. The surface of the 

 sporophore is divided into lozenge-shaped areas each with a projecting 

 stalk bearing a single spore. The nucleus. of these spores, according 

 to Jahn, twice divide by karyokinesis, and finally, when the spore 

 germinates, eight amoeboid bodies are liberated, each of which develops 

 a flagellum and the cluster swims away by the lashing of the flagella. 

 Finally, these cells separate. All other myxomycetes have spores 

 which in germination produce only one myxamoeba. 



Spores of Reticularia which had been dry for eight months germi- 

 nated in thirty-five minutes at a temperature of 21°. Spores exposed 

 to a temperature of 37° for only five minutes germinated in eleven 

 minutes. The spores of Stemonitis flaccida germinated in one hour, 

 those of AmauroclKBte in two and one-half hours, those of Didymium in 

 four to five hours, while it took the spores of Stemonitis ferruginea in 

 wood decoction three to five days to germinate. 



Some remarkable discoveries have been made with regard to an 

 alternation of generations in the slime moulds connected with a so- 

 called sexual act. Jahn, Kranzlin and Olive have worked upon this 

 problem. The generation in all the Myxomycetes, including Ceratio- 

 myxa, with the double chromosome number (8)' (diploid condition) in 

 the nuclei is of short duration. The nuclei of the swarm bodies, amoe- 

 boid bodies and the plasmodium have the single number (4) of chromo- 

 somes. Union of the nuclei to form fusion nuclei with double 



