56 A. E. HILTON OX THE LIFE-PHASES OF MYCETOZOA. 



Then it passes into the spore -forming stage. The plasmodium 

 is gathered up into sporangia, often resembling microscopical 

 fungi, each sporangium containing multitudinous spores. This 

 may be called the dry phase, as the spores escape in the form of 

 very fine dust. When the spores become immersed in water the 

 plasm within them expands by absorption, the fragile shells are 

 ruptured, the plasm-specks emerge as swarm-spores, and the 

 aquatic phase recommences. 



Besides these principal stages there are minor changes, sub- 

 sidiary or contingent. Swarm-spores multiply by bipartition, 

 the process in some cases, if not in all, being repeated. After 

 dividing, they renew their activities. Some become encysted for 

 a while, but presently escape from their shells, without having 

 divided, and resume their movements. The plasmodia also pass 

 at times into a resting-stage, in which they may remain dry 

 and brittle for months, becominc; mobile once more when there is 

 again sufficient moisture. These subsidiary changes, however, 

 we may regard as incidents in the life-cycle rather than phases 

 of it. 



We see, then, that in the main the continuous life-history of 

 Mycetozoa presents us with a series of alternations, in which 

 numbers of plasm-specks (swarm -spores) blend together into 

 amoeba -like plasmodia, and these larger masses divide into 

 innumerable plasm-specks, which recombine as before ; and so 

 on endlessly. It is likewise plainly apparent that these alter- 

 nations depend on varying conditions of the presence or absence 

 of moisture. But we also perceive and for our present purposb 

 this is most important we perceive quite clearly that the 

 essential life -history of Mycetozoa consists, not in the various 

 forms assumed at different stages of progress, but solely in the 

 alternating tendencies of the plasm which produces them. Let 

 me repeat that not in the variety of forms assumed, but in the 

 tendencies of the plasm itself, lies the true inwardness of the life- 

 phases of Mycetozoa. 



Yet the species, numbering less than three hundred, into which 

 this small group is divided display their full share of that striking 

 diversity of shape and colour which makes the study of Nature at 

 once so fascinating and bewildering. Moreover, the classification 

 of the group is largel}' based upon highly microscopical details of 

 structure, which are fairly constant. How, then, it may be asked, 



