32 



MOVEMENTS OF PROTOPLASM IN CELL-CAVITIES. 



in one direction, others 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 onward, leaves a 

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

 between the united bodies. Thus, slimy lumps of protoplasm, which may 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 remarkable fact that these 

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



rMK_ 



Fig. 9.— Creeping Protoplasm. 



creeping about in the same way as the single protoplasts from whose fusion 

 they have arisen. 



Creeping masses of jelly 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 infrequently into bands, cords, and 

 threads, which surround fixed objects, divide, and combine again, forming 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 may be drawn 

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

 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" (Fuligo varians), which are yellow, 

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

 in colour. 



MOVEMENTS OF PROTOPLASM IN CELL-CAVITIES. 



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

 ceU-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 differentiated 

 into distinct individual portions no very lively motion can in general take place 

 LQ the coated protoplast; though it is not to be assumed that it abides completely 



