734 THE POPULAR SCIENCE MONTHLY. 



ductive bodies of the Myxomycetce. When the spore-case has arrived 

 at maturity, it bursts and allows the spores to escape. These are in 

 the form of spherical cells, each included in a delicate membranous 

 wall, and when they fall into water the wall becomes ruptm-ed, and the 

 little cell creeps out. This consists of a little mass of protoplasm with 

 a round central nucleus, inclosing a nucleolus, and with a clear vacu- 

 ole, which exhibits a rhythmically pulsating movement. The little 

 naked spore thus set at liberty is soon seen to be drawn out at one 

 point into a long, vibratile, whip-like flagellum, which by its lashing 

 action carries the spore from place to place. After a time the flagel- 

 lum disappears, and the spore may now be seen emitting and with- 

 drawing finger-like pseudopodia, by means of which it creeps about 

 like an Amceba, and like an Amoeba devours solid particles by ingulf- 

 ing them in its soft protoplasm. 



So far these young A}?iceba-\ike Myxomycetce have enjoyed each an 

 independent existence. Now, however, a singular and significant phe- 

 nomenon is presented. Two or more of these 3fyxamcebce, as they have 

 been called, approach one another, come into contact, and finally be- 

 come completely fused together into a single mass of protoplasm, in 

 which the components are no longer to be distinguished. To the body 

 thus formed by the fusion of the Myxamcebce the name of " Plasmo- 

 dium " has been given. 



The plasmodium continues, like the simple amcebiform bodies of 

 which it is composed, to grow by the ingestion and assimilation of 

 solid nutriment, which it envelops in its substance ; it throws out 

 ramifying and mosculating processes, and finally becomes converted 

 into a protoplasmic network, which in its turn gives rise to spore-cases 

 with their contained spores, and thus completes the cycle of its devel- 

 opment. 



Under certain external conditions, the Myxomycetce have been ob- 

 served to pass from an active mobile state into a resting state, and this 

 may occur both in the amcebiform spores and in the plasmodium. 

 When the plasmodium is about to pass into a resting state, it usually 

 withdraws its finer branches, and expels such solid ingesta as may be 

 included in it. Its motions then gradually cease, it breaks up into a 

 multitude of polyhedral cells, which, however, remain connected, and 

 the whole body dries into a horny brittle mass, known by the name of 

 " sclerotium." 



In this condition, without giving the slightest sign of life, the 

 sclerotium may remain for many months. Life, however, is not de- 

 stroyed ; its manifestations are only suspended; and if after an indefinite 

 time the apparently dead sclerotium be placed in water, it immediately 

 begins to swell up, the membranous covering of its component cells 

 becomes dissolved and disappears, and the cells themselves flow to- 

 gether into an active amoeboid plasmodium. 



We have already seen that every cell possesses an autonomy or in- 



