428 SECOND PART.— MYCETOZOA. 
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!. 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 a. 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. 

1 Icon. Fung. II, Fig. 87 2. 
