428 SECOND PART.- MFCETOZOA. 



their vitality for more than two months ; how soon life becomes extinct in them has 

 not been ascertained. If placed again in water, they return to the motile swarming 

 state, and the more quickly the shorter the period of desiccation. Those of 

 Perichaena liceoides cast off their outer membrane under these conditions. 



The thick-walled cysts and sclerotia are resting-states of plasmodia. The 

 former were examined by myself in isolated cases in Fuligo, and Cienkowski 

 followed them through the whole course of their development in Perichaena liceoides. 

 The cysts were formed by young plasmodia in both species. According to Cien- 

 kowski's observations the plasmodium divides by the rending of its branches into 

 pieces of very unequal size, which draw in their processes and assume the shape of 

 smooth spheres. Then a membrane of considerable thickness forms on the surface 

 and becomes rough and wrinkled and assumes a dark-brown colour. Within this 

 membrane the protoplasm contracts still more and forms on its surface a second 

 coat with a double-contour. If placed in water after drying for several weeks the round 

 bodies remain first of all unchanged for some weeks, and then the protoplasm begins 

 to display slow undulating movements and at length swells up, makes a hole in the 

 surrounding coats, and slowly emerges from them with all the characters of a 

 plasmodium. 



The sclerotia are the resting-states of full-grown plasmodia. They have been 

 observed in Didymium leucopus and D. difforme, D. Serpula, Fuligo, Physarum sinu- 

 osum, Perichaena liceoides and in a number of Physareae which have not been more 

 precisely determined, and perhaps also by Corda in Stemonitis 1 . Some of them are 

 the forms on which Persoon based his fungal genus Phlebomorpha. 



When their formation begins the plasmodium draws in its slenderer processes 

 and assumes the shape of a sieve-like plate, or in Fuligo of a small tuber a few 

 millimetres in diameter and with irregular prominences on its surface ; the granules 

 become distributed uniformly through the fundamental substance, the solid ingesta are 

 extruded, the movement gradually ceases, and the whole body breaks up into an 

 innumerable quantity of roundish or polyhedric cells with an average diameter of from 

 25 to 40 /i. The body becomes at the same time of a wax-like consistence and 

 dries into a brittle horny mass, resembling the sclerotia of many Fungi. 



Each cell chiefly consists of a firm protoplasm which incloses vacuoles varying in 

 size and number, and a pigment and granules distributed in the same manner as in the 

 motile plasmodia, and shows a sharply limited marginal layer. Nuclei are there no 

 doubt, though they have not as yet been observed. In the strongly developed sclerotia 

 of some species (Fuligo, Didymium Serpula) the protoplasm is surrounded by a distinct 

 colourless membrane, which in both the species mentioned shows the reaction of 

 cellulose with iodine and sulphuric acid or with Schulze's solution. The membranes 

 are firmly attached to one another, either immediately or, as in Fuligo, by a homogenous 

 intermediate substance which softens in water. In small weakly developed specimens 

 of the above species and in all sclerotia that have as yet been examined in other 

 species, as for instance in Didymium difforme, no distinct membranes can be seen 

 round the protoplasm. 



Icon. Fung. II, Fig. 87 b. 



