32 Di'. Wallich on Endogenous as distinct from 



when the creature is subjected to undue pressure, or its move- 

 ments are impeded by foreign matter, tlirough which it has 

 difficulty in forcing a passage. Whereas under perfectly 

 natural conditions the creature is in all probability able 

 either to push aside the obstructing matter or select another 

 route. When closely confined between the glass slide and 

 cover it has no such easy alternatives. Therefore all that 

 can be safely inferred from watching the behaviour of an 

 artificially or accidentally-divided and enucleate portion of an 

 Amoeba is, that being endowed, in common with the rest 

 of the body, with a diffused nervous faculty, this portion 

 is, for some unknown reason, more detrimentally affected by 

 the shock sustained by it than the remaining portion which 

 possesses the nucleus. 



Why the possession of the nucleus (which is never a per- 

 manently fixed organ in the Amoehce) should carry with it a 

 superior degree of vitality, it is as yet impossible to say with 

 any certainty. But, as first shown in my papers on "Amoeba 

 villosa and other Indigenous Rhizopods," in the ' Annals ' 

 for May and June 1863 (pp. 366, 436, and 437), and also in 

 subsequent numbers of the same journal, there evidently 

 subsists an intimate relation between the nucleus and the 

 unique persistent area of the Amosban surface constituting its 

 posterior region, whether this region be covered with any of 

 the varieties of villous appendage or consist merely of a 

 specially differentiated outer layer of sarcode — the intimacy 

 of this relation becoming almost certain, firstly, from the 

 specially differentiated area never undergoing Amoebasis (as 

 every other part of the sarcode body does) or taking part in 

 the general pseudocyclosis ; secondly, from the nucleus, after 

 participation for a time in the general pseudocyclosis, 

 almost always coming to rest in the vicinity of the area in 

 question ; and, thirdly, from the contractile vesicle, after 

 participation temporarily in the pseudocyclosis, also coming 

 to rest and generally discharging its contents close to the same 

 region. 



The extraordinary degree of vitality possessed by tlie pos- 

 terior portion of Amosba is very signally manifest when lump 

 after lump of the anterior portion is bitten off by some creature 

 that preys on it, as, for instance, Coleps Mrtus, or another 

 Amoeba with cannibal proclivities. Under these circumstances, 

 if the nucleus and specially differentiated area remain intact, 

 the original mass, although reduced to less than even half its 

 normal bulk, will, in the course of an hour or so, move away 

 as energetically as if no injury whatever had happened to it. 

 Now this is precisely the condition of things existing when 



