336 Dr. G. C. Wallich on the Distinctive Characters and 



recognized as analogous, if not identical in their origin, with the 

 naked nuclear masses described and figured by me in a previous 

 Number of the ' Annals ' as occasionally resulting from the extra- 

 capsular subdivision of the granular contents of the primary 

 nuclear cell (Annals, May 1863, p. 368). 



The presence of these dead and empty frustules of Nitzschia 

 is well worthy of note, as yielding evidence, almost tantamount 

 to proof, that their soft contents had undergone digestion, and 

 hence that they had been received into the interior of the Amceba 

 prior to encystation and desiccation; whilst the fact of their 

 being commonly taken as food by the Amoeba is manifest from 

 the numbers of Amcebce now living on the material, that contain 

 within their endosarc frustules full, as also partially relieved, of 

 their endochrome. 



It may be recollected that, in the same Number {loc. cit.), I 

 expressed doubts as to the normal investiture of any Amoeba 

 by a membranous ectosarc, and inclined to the view that the 

 single example of such investiture which had fallen under my 

 notice up to that period betokened encystation. The strongest 

 confirmation of that opinion is hence afforded; for not only were 

 empty and effete cysts now met with, but a few examples of cysts 

 in which the sarcode-mass, although apparently in a deteriorated 

 state, had recovered a sufficient degree of contractility to pro- 

 duce distinct changes in their form. Of the ultimate fate of 

 these revivified cysts I have not as yet been able to satisfy myself. 

 There are reasons, however, for supposing that they are only 

 destined to afford protection to the reproductive elements until 

 such period as the latter are in a fit condition to be set at liberty. 

 It would also seem probable that the encystation of Amoeba does 

 not take place, as a matter of course, at certain seasons, but only 

 when the normal conditions of the creature's existence become 

 impaired or altogether deficient — the increased consolidation 

 of the external layer being the exceptional i-esult of prolonged 

 contact with the vitiated medium around, and the cessation 

 of that reciprocal interchange between endosarc and ectosarc, 

 described by me under the name of Amcebasis, which is con- 

 tinually going on in the healthy state of the organisms. That 

 such is the case may be reasonably inferred from the absence of 

 anything like the encysted condition in the specimens of Amoeba 

 villosa which have now been seven mouths under close observa- 

 tion, and carefully protected from desiccation. Should encysta- 

 tion in the remaining Hampstead material follow on slow de- 

 siccation being permitted to take place, the proof required will 

 be complete. 



AVaut of time and space preclude me from entering into full 

 details respecting the several modes in which, in addition to 



