PROTOPLASM 



feet "), and the general chararacter of such motion is called 

 " amoeboid." ^ 



The living substance, protoplasm,^ has been termed a "jelly," 

 a word, however, that is quite inapplicable to it in its living 

 state. It is viscid, almost semi-fluid, and may well be compared 

 to very soft dough which has already begun to rise. It resembles 



Fig. 1. — Amoeba, showing clear ectoplasm, granular endoplasra, dark nucleus, and lighter 

 contractile vacuole. The changes of form, a-f, are of the A. Umax type ; g, h, of 

 the A. proteus type. (From Verworn.) 



it in often having a number of spaces, small or large, filled with 

 liquid (not gas). These are termed " vacuoles " or " alveoles," 

 according to their greater or their lesser dimensions. In some 

 cases a vacuole is traversed by strands of plasmic substance, just 

 as we may find such strands stretching across the larger spaces 

 of a very light loaf ; but of course in the living cell these are 

 constantly undergoing changes. If we " fix " a cell (i.e. kill it by 



prolonging the front of the pseudopodium, while the material of the lower surface is 

 brought up behind. H. S. Jennings, Conir. to the Study and Behavioxir of the Lower 

 Organisms, 1904, pt. vi. p. 129 f., "The Movements and Reactions of Amoeba." 



^ If the protoplasm contains visible granules, as it usually does, within a clear 

 external layer, we see that these stream constantly forwards along the central axis 

 of each process as it forms, and backwards just within the clear layer all round, 

 like a fountain playing in a bell-jar. This motion is most marked when a new 

 pseudopodium is put forth, and ceases when it has attained full dimensions. 



2 We use as a corresponding adjective the term "plasmic." 



