and Reproductive Phenomena of the Amoeban Rhizopods. 455 



as it were, by the artificial impulse received on the discharge 

 of the contractile vesicle ; pseudopodia ai'e projected and with- 

 drawn, and, as a necessary consequence of these movements, 

 pseudocyclosis goes on ; food-particles are incepted, effete 

 matter extruded at the point of least resistance — namely, in the 

 midst of the villous organ ; and, following as a natural result 

 from these combined changes and the more subtle actions they 

 involve within the body, the phenomena of amoebasis are esta- 

 bhshed (see Plate VIII. figs. 4 & 5). 



Although it would appear, at the first glance, that the villous 

 appendage constitutes the most highly differentiated portion 

 of the Amoeban structure, since the contractile vesicle in- 

 variably discharges, and all effete objects are extruded, in its 

 midst, the reverse is probably the case, inasmuch as, the con- 

 tinuity of the endosarc in this region being constantly disturbed 

 by the causes just named, time is not allowed it to attain the 

 same degree of consolidation that is attained by the rest of the 

 surface. It must be borne in mind that the coalescence of the 

 pseudopodia is rare in Amoeba. Indeed it hardly ever takes place 

 except under an effort to envelope some living object, or when 

 the surface is broken, and a portion of the ectosarc driven back 

 along with it into the interior of the body*, by the admission of 

 some large food-particle. 



But inasmuch as inception of food is only an occasional act, 

 the disturbance of the ectosarc, which is its necessary conse- 

 quence, must also be occasional. On the other hand, the con- 

 tractile vesicle is constantly discharging itself at a single spot, 

 namely, in the midst of the villous appendage ; and it is here that 

 the effete residue of every object incepted, either for food or by 

 accident, is extruded. Moreover, whilst the inception of a food- 

 particle can very rarely take place twice consecutively at the 

 same spot, every act of extrusion does so ; and this being the 

 case, it is easy to perceive why the consolidation of the external 

 layer of sarcode (ectosarc), being the result of contact with 

 water, and dependent in degree on the period of exposure, should 

 be greater in every other part of the body than in the villous 

 region. 



Again, it thus becomes easy to understand why the contractile 

 vesicle discharges itself, and effete matters are extruded, in the 

 villous region. It has been shown that the circulation of the 

 contents of the sarcode-body is not a special vital act, but due 

 to its polymorphism. Now contractility is the inherent property 



* On two occasions I have seen a full-grown Arcella so incepted, not 

 through an aperture extemporized, but evidently in the same way that a 

 small object, if pressed against an inflated caoutchouc capsule, would push 

 before it a portion of the wall. 



