the Distinctive Characters in Amoeba. 133 



nerally does^ a period varying with its size, from a few minutes 

 to upwards of an hour. 



Here, then, we have the strongest evidence that the degree 

 of consohdation necessary to estabhsh the differentiation of the 

 ectosarc, so as to permit a tubule or excretory passage to be 

 formed, the walls of which do not instantly coalesce as water 

 does around any heavier object dropped into it, but close slowly 

 and gradually from within outwards, is due to the mere con- 

 tact of the fluid which is invariably present whenever such 

 tubules or excretory orifices are observable ; whereas, in those 

 cases in which the watery matter has been removed by digestive 

 absorption prior to the discharge of an effete mass, the latter 

 passes out thi'ough the substance of the ectosarc, and without 

 the production of any passage whatever. In this case, more- 

 over, the ectosarc closes around the effete body almost as rapidly 

 as that body can escape. 



When foreign substances appear within the endosarc, unsur- 

 rounded by any appreciable vacuole, I have almost invariably 

 found them to consist either of mhieral particles or the effete 

 remains of food objects. But this by no means proves that they 

 obtained entrance into the interior without any accompanying 

 water, but only that the latter has been absorbed ; for, in view 

 of the conditions and the manner in which a foreign body is 

 invariably engulfed, it seems almost impossible to conceive the 

 entrance to take place without the simultaneous entrance of a 

 portion of the medium in which both the animal and the food- 

 particle are sustained. 



The reciprocal convertibility of endosarc and ectosarc, for 

 which I would propose the term amoebasis*, constitutes, as it 

 appears to me, a very important and definite distinction between 

 the animal and the vegetable protoplasm, — the permanent dif- 

 ferentiation of the true cell-wall of the protophyte rendering 

 necessary nutrition by endosmotic absorption, whereas in the 

 Protozoan the continual interchange of parts enables the animal 

 to incept organic matter for food. But, as I shall endeavour to 

 show on a futui'e occasion, this power of incepting solid organ- 

 ized substances does not present itself distinctly in the two lower 

 orders into which I propose to divide the Rhizopods, but only 

 in the third or highest order, in which the contractile vesicle 

 makes its appearance for the first time; whilst, as already 

 mentioned in my paper in the ' Annals ' for June, p. 440, if a 



* 'Aftot/3i7 (reciprocity). It is somewhat singular that the word from 

 which the generic name of Amoeba is derived, and which was selected with 

 reference to the alternate expansion and retraction of the pseudopodia, 

 should in reahty express the precise action now referred to as being in- 

 volved in the sarcode substance. 



