THE LIFE-PHASES OF MYCETOZOA. 



By a. E. Hilton. 



{Read April 26f7/, 1910.) 



In his 3Ionograph of the Jfi/cetozoa (1894) the late Mr. Arthur 

 Lister expressed his belief that the numb9r of species already 

 known was not likely to be largely added to by gatherings from 

 any hitherto unsearched regions ; and in the first volume of The 

 Cambridge Xatural History (1906) Dr. Marcus Hartog observed 

 that with the exception of one species {Fuligo varians), which is a 

 pest in tan-pits, the interest of the group is entirely biological. 

 These remarks, taken together, testify to the fact that within 

 the convenient limits of a comparatively small group we have an 

 exceptional opportunity for studying life-phenomena, by reason, 

 of the processes being less obscured than in many other 

 organisms. 



Briefly, the life-cycle of the Mycetozoa has three principal 

 phases an aquatic, an amoeboid, and a spore-forming stage. 



In the aquatic stage the individual swarm-spore is a speck of 

 plasm, with nucleus, vacuoles, and a flagellum so small that to be 

 seen clearly a magnification is necessary of from 500 to 1,000 

 diameters. At times the swarm-spores move about in the water 

 with great rapidity. 



In the phase which follows, which is usually aquatic only at 

 the outset, a plasmodium is formed by the fusion of many swarm- 

 spores, this process being a distinguishing characteristic peculiar 

 to the Mycetozoa alone. Amoeba-like, the plasmodium creeps 

 about within the substance of decaying wood or upon other 

 rotting vegetation, on which it feeds. At this stage it may be 

 either microscopical in size or spread over a considerable surface 

 in the form of an irregular and extended network with a con- 

 stantly changing outline. To keep it mobile, air and moisture 

 are both essential ; but as it matures it develops a tendency to 

 leave the damper and seek the drier places, where it concentrates 

 and comes to rest, 



JouRN. Q. M. C, Series II Xo. 67. 5 



