416 PKOr. ALLMAN ON THE RECENT RESEARCHES 



Myxomycetcd have been observed to pass from an active motile 

 state into a resting state ; and this may occur in both swarm- 

 spores and Plasmodium. In the case of the swarm-spores, these 

 bodies, when passing into the resting state, assume a spherical 

 form, and become surrounded by a delicate membrane or by a firm 

 external layer of thin protoplasm. In this condition, in which 

 they constitute the " microcysts " of Cienkowski, they may 

 remain, after complete desiccation, in a dormant state for more 

 than two months ; and on being again placed in water they soon 

 resume their original activity. 



But the Plasmodium itself, as well as the swarm-spore, may pass 

 into a resting state. After withdrawing its finer branches, and 

 expelling such solid ingesta as may be included in it, its motions 

 gradually cease, it breaks up into a multitude of polyhedral cells, 

 and the whole body dries into a horny brittle mass, to which the 

 term " sclerotium " has been given. 



It sometimes happens that the plasmodium, instead of forming 

 a continuous sclerotium, breaks up into separate pieces of very 

 unequal size, which withdraw their projecting branches and assume 

 the form of smooth spheres, round which a thick membrane is 

 excreted. "Within this outer membrane the protoplasm contracts 

 and forms on its surface a second membrane. To these cell-like 

 bodies Cienkowski has given the name of " thick-walled cysts." 



Both these resting states of the plasmodium may, like that of 

 the swarm-spores, undergo complete desiccation, and thus con- 

 tinue for many months in an inactive state without losing their 

 vitality. When the dry sclerotium is placed in water, it imme- 

 diately swells up, and after a time its cells again flow together into 

 an amoeboid protoplasm. So also when the thick-walled cjsts, after 

 remaining long desiccated, are similarly treated, their membrane 

 will become ruptured, and the contained protoplasm will escape 

 and begin to throw out pseudopodia and glide about like an Atnoeia, 

 and engulf within its substance foreign bodies for nutriment, 

 while several may unite by fusion into larger amoebiform masses 

 and thus give rise in their turn to new plasmodia. 



In a subsequent paper* Cienkowski describes the plasmodium 

 of an unknown My xomycete which occurs in fresh water in the form 

 of a sarcode network, and which has enabled him to add some in- 

 teresting facts to our knowledge of the plasmodium. 



* Cienkowski, "Ueber einige Rhizopodeu und vervTandte Organismen," 

 Archiv f. mikr. Anat. 1875. 



