440 Dr. G. C. Wallich on Amoeba villosa 



coalescing to constitute a single cavity, or, as happens occasion- 

 ally, each undergoing a separate systole. This- 1 maintain could 

 not possibly take place except under the conditions I have en- 

 deavoured to describe. 



The vacuoles within which organic substances, or animalcules, 

 incepted for food become amenable to the digestive process are 

 similarly constituted ; and if what has been advanced by me in 

 my previous paper be correct (that is to say, if endosarc and 

 ectosarc are not permanent portions of the Rhizopodal structure, 

 but mutually and temporarily convertible one into the other), it 

 is manifest that the higher state of differentiation exhibited by 

 the vacuolar wall is wholly due to a like cause, namely, contact 

 with a portion of the surrounding fluid. 



I am well aware that the permanently visible villous area of the 

 Hampstead Amoeba appears to militate in some measure against 

 the universal correctness of this hypothesis. But I have ah'cady 

 stated that this species can hardly fail to be regarded as em- 

 bodying the highest type of llhizopod life, and as bridging over 

 the hiatus between true Rhizopod and true Infusorial organi- 

 zation. If a boundary exists at all between these two great 

 groups of the Protozoa, it will, I think, be found to consist in 

 this — that whereas in the Ehizopods there is no permanent 

 orifice for the inception and extrusion of foreign or efifete matter, 

 and the endosarc and ectosarc are not permanent portions of the 

 organism, but, as already maintained, mutually convertible one 

 into the othei', in all mature Infusorial forms permanent orifices 

 occur for the inception and extrusion of such matter, and there 

 is no convertibility of parts once established*. Hence, even 

 granting, for the sake of argument, that the villous patch in 

 Amoeba villosa is not only permanent in position as regards the 

 rest of the body, but, in a like sense, permanent in composition 

 during the entire period of the individual's existence, I contend 

 that we should not be warranted, on this ground alone, in press- 

 ing such an objection. But I am by no means prepared to allow 

 that such a permanent condition of the villous region does exist, 

 inasmuch as it appears to me to be far more probable and conform- 

 able with the phenomena referred to, to assume that a slow but 

 constant interchange of protoplasmic matter takes place there, 

 as it does, although more rapidly and perceptibly, in the other 

 portions of the structure. 



During the bygone month I have seen numerous examples of 

 the infundibuliform excretory tubule of A. villosa. But I have 

 likewise been able to satisfy myself that this tubule is an extem- 



* Asplanchna furnishes no valid objection to this generahzation, even if 

 we hesitate to accept the most recent views promulgated regarding its 

 structure j for one orifice may serve both purposes. 



