192 



THE AMERICAN MONTHLY 



[October, 



another is moving past them. In 

 short, the effect is similar to that 

 which would be produced were a 

 transparent bladder or caoutchouc sac, 

 containing granular bodies of greater 

 specific gravity than the viscid fluid 

 within which they were sustained, to 

 be slowly rolled along a plain surface. 

 In such a case it is obvious that only 

 the granules on the upper or. free as- 

 pect of the sac would be carried on- 

 wards, and that, having arrived at 

 the most advanced point, they would 

 be deposited (by their own weight) 

 and remain stationary in common 

 with that portion of the sac on which 

 they rested, until the rest of the mass 

 should again have flowed over them, 

 causing them now to appear at the 

 posterior extremity, when they would 

 once more be carried along as before. 

 * * * The essential attributes of 

 sarcode, namely extensibility and 

 contractility, coupled with the poly- 

 morphism evident in every example 

 in which definite form is not partially 

 maintained by the presence of a shell 

 or test, necessarily involve the power 

 of retracting as w^ell as projecting 

 these processes. Whereas the tenac- 

 ity of the substance is not such that a 

 pseudopodium once projected can be 

 retracted toward the body in the same 

 way that a piece of rope thrown for- 

 wards from a given point can be 

 hauled in again, inch by inch. In 

 the broad pseuopodium of Aniceba^ 

 as also in the attenuated filaments of 

 the Foraminifera, or the still more 

 subtle filaments of AcantJiometra or 

 EnglypJia^ the process is the same, 

 and is bi^ought about by a reciprocal 

 outward and inward flow of the sar- 

 code substance ; and thus the granu- 

 lar particles are merely the passive 

 exponents of a vital force which acts 

 quite independently of them. For 

 these reasons I would still regard the 

 circulation of granules in the rhizo- 

 pods as a pseudocyclosis, analogous, 

 I grant, in appearance, but not in 

 origin, to the cyclosis observable in 

 certain vegetable cells, as, for ex- 

 ample, in Tradescantia.' (Further 



Observations on the Distinctive Char- 

 acters and Reproductive Phenomena 

 of the Amoeban Rhizopods. By the 

 same author. Annals and Mag. 

 Nat. Hist., Nov., 1863.) 



' It is deserving of special notice, 

 moreover, that the facility with which 

 coalescence takes place between the 

 pseudopodia, and the adhesive faculty 

 of the ectosarc, are such mutually 

 dependent conditions as to be insepa- 

 rable. In Lieberkiihnia. the Fora- 

 minifera, and the Polycystina, these 

 characters are at a maximum. In 

 Amceba they are at a minimum, and 

 consequently denote the closeness of 

 the relation existing between the de- 

 gree of diflerentiation, as thus mani- 

 fested, and the presence or absence 

 of a true nucleus and contractile 

 vesicle. The higher the degree of 

 differentiation, or, in other words, 

 the higher the grade of the organism , 

 the more completely does Amcebasis* 

 take place in it. In Amceba., which 

 occupies the highest position amongst 

 the true rhizopods, the distinction 

 bet\\'een the external and internal 

 portions of the sarcode-substance is 

 at a maximum, and hence there exists 

 an opposite condition to that present 

 amongst the Herpnemata (the lowest 

 order of rhizopods in my classifica- 

 tion) , and we meet with the smallest 

 amount of inclination to coalescence, 

 and the least degree of adhesive vis- 

 cidity in the ectosarc. Lastly, and 

 equally worthy of note, is the fact that 

 the lower the degree of differentiation 

 of the sarcode-substance, the more 

 distinctly is the pseudocyclosis of 

 granules observable, and the more 

 completely does it approach, and even 

 involve, the immediate surface of the 

 pseudopodia ; being dependent as al- 

 ready shov\^n, not in an inherent fac- 

 ulty of the protoplasm to circulate, 

 but on the inherent contractile power 

 of sarcode, by means of which.a con- 



*'lheterm applied by me to denote the reciprocal 

 convertibility ol endosarc and ectosarc. As stated 

 in another paper, it i« singular that the word 'Ainoibe' 

 from which the generic name AtiKjcba is derived, sin- 

 nifies reciprocity 01 return, and yet that the true sig- 

 nificance of the phenomend should not have been 

 recognized. 



