32 



MOVEMENTS OE I>K( »TOPJ.ASM IX CELL-CAVITIES. 



in one direction, otiiers on the opposite side are retracted, and the protoplast as 

 a whole glides over the intervening space like a snail without its shell. The 

 analogy is all the more exact since the protoplast, as it glides on\\ard, leaves a 

 slimy trail in its wake, so that the latter is marked by a streak resenihling the 

 track of a snail. When two or more of these creeping protoplasts, or plasmodia, 

 meet, they merge into one another, flowing together somewhat in the same way 

 as two oil-drops on water coalesce into one — leaving no distinguishable boiuidaries 

 between the united bodies. Thus, slimy lumps of protoplasm, which niay attain 

 to the dimensions of a closed or open hand, result from the coalescence of great 

 numbers of minute protoplasts. And it is a very remarkaltle fact that these 

 Plasmodia can themselves change their form, putting out lolies and threads, and 



Fig. 9.— Creeping Protoplasm. 



creeping about in the s;uue way as the single pi'otoplasts from whose fusion 

 they have arisen. 



Creeping masses of jellj^ sometimes move in the direction of incident light; at 

 other times they avoid light and hide in obscure places, wriggling through the 

 interstices of heaps of bark or into the hollows of rotten trunks: or they may 

 creep up the stems of plants, or glide over the brown earth in a viscous condition. 

 On these occasions they resolve themselves not infrecjuently into bands, cords, and 

 threads, which surround fixed objects, divide, and combine again, foiming a net- work 

 of meshes, or else perhaps frothy lumps like cuckoo-spit. If foreign bodies of small 

 size are enmeshed by the viscous threads of the reticulum, they maj^ be drawn 

 along by the protoplasm as it creeps; and if they contain nutritive material, thej^ 

 may be eaten up and absorbed. Plasmodia are, for the most part, colourless, but 

 some are brightly tinted; in particular may be mentioned the best-known of all 

 plasmoid fungi, the so-called "Flowers of Tan" (Fidigo variaiif^), which are j-ellow, 

 and Lycogala Ejndendron , which comes out on old stumps of pines, and is vermilion 

 in colour. 



MO\'EMENTS OF PROTOPLASM IN CELL-CAVITIES. 



In the case of a protoplast which is not naked, but clothed with an attached 

 cell-membrane, the movements are limited to the space included by the membrane, 

 that is to say to the cell-cavity. Until the protoplasmic cell-body is difierentiated 

 into distinct individual portions no very live!}' motion can in general take place 

 in the coated protoplast: though it is not to be assumed that it abides completely 



