108 Dr. A. Gi'uber's Contributions to the 



behaviour of Amoeba tentaculata, and its conditions would per- 

 fectly agree with those occurring in A. verrucosa, which is so 

 abundant and has been so often described. 



But while in the latter we miss true pseudopodium-forma- 

 tion, both in the resting state and during flow, we are sur- 

 prised here by seeing line protophismic filaments make their 

 appearance at different parts of the body. These are thin 

 processes of equal breadth throughout, which stand out from 

 the body, sometimes in one place, sometimes in another, and 

 bend to and fro as if feeling about, often curve into a bow, 

 but generally remain extended pretty straight. It first struck 

 me that these pseudopodia did not, as in other Amoeba', spring 

 from the protoplasmic body in the shape of fingers gradually 

 becoming thinner, but that small conical elevations of the 

 body served as their base, and that they rose from these with 

 a distinctly marked separation. When such pseudopodia with 

 their supports were very numerous, they gave tlie Amoeba a 

 very peculiar appearance, which I have attempted to represent 

 in fig. 1. 



The business now was to discover a reason for the peculiar 

 behaviour of the pseudopodia ; and in this I very soon suc- 

 ceeded by the employment of immersion systems (Hartnack, 

 Ko. X. or Seibert homogeneous imm.). It proved that the 

 whole Amoeba is enveloped by a fine layer of denser substance, 

 consequently a membranaceous cortical layer, which causes 

 the periphery of all its humps and processes to appear distinctly 

 double-contoured. 



In the case of the terrestrial Rhizopods like A. tentaculata 

 described by Greeff *, the idea of a similar tougher cortical 

 layer could not be avoided, as also in that oi Amoeba verrucosa, 

 which is so often mentioned. In the case of the latter, indeed, 

 I did not succeed in detecting any thing of the kind ; but 

 Leidy t says, '' A striking peculiarity of Amoeba verrucosa is, 

 that the outlines of the body, the pseudopodal expansions, 

 and the wrinkles of the surface often appear defined with 

 partial or interrupted double lines, as if the animal were in- 

 vested with a delicate membrane (pi. iii. figs. 1^ 2, 7, 28, 

 29)." It is, however, certainly such a membrane, or rather 

 membranaceous thickening of a fine cortical layer, that we 

 find in Amoiba tentaculata. 



Directly within this firmer envelope lies the soft internal 

 sarcode-mass ! If a pseudopodium is to be jsushed forth, the 

 enveloping layer must first be broken through. This, how- 

 ever, ofiers some resistence, and is consequently pushed out in 



* Arcliiv f. milii". Aiiat. Bd. ii. 



t Leidy, 'Freshwater Eliizopods of North America,' p. 55. 



