THE SARCODINA 



85 



is poured out upon the free surface of the protoplasmic body, where 

 it produces a local diminution of surface tension, and in this way sets 

 up an extension centre together with forward movement." 1 



The origin of a pseudopodium, according to this conception, is in 

 the ectoplasm, and the rapidity of a pseudopodium-formation is 

 increased by the peculiar "fountain currents" char- 

 acteristic of most pseudopodia. As observed by 

 Butschli, an advancing stream of granules flows 

 through the centre or axis of the growing pseudopo- 

 dium, while near the tip back-running currents like 

 the falling drops of water in a fountain surround the 

 central stream (Fig. 47). " In the formation of a Fig.47.— Diagram 

 finger-shaped pseudopodium of Amceba proteus," says ° fth e movements of 



-j, , .. . . . , , . the endoplasm gran- 



butschu, it can be seen that the current which u i es in an advanc- 

 traverses the axis of the pseudopodium and flows in s pseudopodium 



n • 1 r .. of Amceba proteus. 



away on all sides from its tip, comes to rest at a [butschli.] 

 very short distance behind the tip, — a circumstance 

 which in any case is extremely favorable to the rapid outgrowth of 

 the pseudopodium, in contradistinction to the relations that obtain in 

 the drops of foam, since the protoplasm that has come to rest is 

 heaped up and the pseudopodium grows in this way." 2 



Rhumbler ('98) attempts to explain the formation of new ectoplasm 

 and the increase in surface of an advancing pseudopodium through 

 the hardening effect of water upon protoplasm, a fact which has long 

 been recognized (Butschli, Pfeffer). An advancing pseudopodium of 

 Amceba proteus, if properly fixed and stained, shows an advanced mass 

 of endoplasm broken through the walls of ectoplasm. 3 



The outer ectoplasm has a firm 

 consistency, and, as Rhumbler dem- 

 onstrated by treatment with diluted 

 caustic potash (Fig. 48), may 

 be isolated from the endoplasm. 

 Nevertheless, it is converted into 

 streaming endoplasm again. The 

 astric conversion of ectoplasm into endo- 

 plasm, which was early noted by 

 Engelmann ('79) and recently by 

 Penard, Pfeffer, Verworn, Butschli, and others, takes place accord- 

 ing to Rhumbler at all times. It is particularly well shown in 

 Amceba limicola Rhumbler, or A. blattcz Butschli, where the eruptive 

 pseudopodium incloses a definite portion of the old ectoplasm, which 

 soon disappears and becomes lost in the endoplasm. Both Butschli 



1 Biitschli, loc. cit., English translation, pp. 310-31 1. 



- Loc. cit., p. 312. 3 Cf. Fig. 10, A, p. 36. 



Pig. 48. — The ectoplasm (e) and 

 vacuoles (0) of Amosba verrucosa after treat- 

 ment with KOH. [RHUMBLER.] 



