Indigenous Form of Amoeba. 289 



lav particles of endosarc within such of the coalesced villi 

 as, from their size, rendered observation practicable. 



As a general rule, the contractile vesicle and nucleus maintain 

 a position close to the villous patch, even whilst the animal is 

 moving — the former organ being in close proximity to it, and 

 sometimes appearing to discharge itself, by the usual systolic 

 action, at a spot within the villous surface. But now and then 

 both nucleus and contractile vesicle move slowly round with the 

 mass of circulating particles. The villous area, however, retains 

 its position in relation to the rest of the body. 



In some specimens the contractile vesicle presents an appear- 

 ance of the most delicate reticulation, resembling that described 

 as occurring on the external surface o£Actinophrys, and depending 

 probably on a similar cause, namely, the occurrence of a number 

 of minute vacuoles. The contractile vesicles occasionally sub- 

 divide into several smaller cavities, as constantly happens in 

 other forms ; and these either coalesce prior to collapse, or they 

 collapse separately. But no sinuses of the kind described by 

 Carter in Paramecium aurelia and other Infusoria are discernible. 

 Vacuoles are frequent, and in some cases of sufficient size to 

 contain large diatoms. 



The nucleus consists of a pale grey-coloured spherical mass of 

 granules, towards the centre of which may occasionally be de- 

 tected a minute clear nucleolus. It is contained within a hya- 

 line and somewhat elongated vesicular cavity, but never oc- 

 cupies the entire area of the latter. 



Dilute alkaline and acid solutions cause the body at once to 

 assume a more or less spherical shape, and the granular contents 

 to close up into a central mass, leaving a broad hyaline border 

 around the entire surface, as described by Auerbach in Amoeba 

 bilimbosa. But these reagents fail to render apparent anything 

 like the double outline, indicative of a definite membranous 

 envelope, alluded to by that author. It is worthy of note, 

 however, that, under imperfect adjustment of focus or want of 

 due care in illumination, the semblance of a double outline can 

 be evoked. 



Some of the specimens of the Hampstead Amo?ba are of extra- 

 ordinary dimensions, the largest attaining a diameter of no less 

 than i^jth of an inch. The villi, in their quiescent state, seem 

 to be about 1;3 ^ 00 th of an inch in average length. 



In a solitary example, the villous patch constituted a nearly 

 circular brush-like tuft at the extremity of a cylindrical pedicle 

 of hyaline sarcode ; and at its centre was a minute vacuole- 

 like space. I kept my eye on this specimen for nearly a quarter 

 of an hour without perceiving this structure alter in anywise, — 

 the prehensile power of the villi seeming to be either suspended 



