and Reproductive Phenomena of the Amoeban Rhizopods. 451 



nifei'a, and the Polycystina these characters are at a maximum ; 

 in Amoeba they are at a minimuai, and consequently denote the 

 closeness of the relation existing between the degree of differentia- 

 tion, as thus manifested, and the presence or absence of a 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 Amoeba, which occupies the 

 highest position amongst the true Hhizopods, the distinction 

 between the external and internal portions of the sarcode-sub- 

 stance is at a maximum, and hence there exists an opposite 

 condition to that present amongst the Herpnemata or lowest 

 order (see ' Annals ' for June, p. 439), and we meet with the 

 smallest amount of inclination to coalescence and the least de- 

 gree of adhesive viscidity of the ectosarc. 



Lastly. And equally deserving of notice 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 im- 

 mediate surface of the pseudopodia — being dependent, as already 

 shown by me (Annals, November, p. 332), not on a vital ten- 

 dency to circulate inherent in the protoplasm or its granules, 

 but on the inherent contractile power of sarcode, by means of 

 which a constant interchange takes place between the interior 

 mass and the external layer, and an equable distribution of 

 nutritive material is secured in the bodies of the most rudiment- 

 ary and testaceous types. When it is borne in mind that in 

 none of the families of Rhizopods is the circulation uninterrupted, 

 but that it not only continually varies in rate, but very frequently 

 ceases altogether for a time, it will, I think, be allowed that 

 any analogy between the phenomena and a special circulatory 

 force is altogether discountenanced ; whilst we further discern 

 that the stoppage of a circulating granule, its occasional transfer 

 from one pseudopodium to another, and its subsequent advance 

 or retrogression towards the parent body (on which so much 

 stress has been laid by those who advocate the operation of a 

 special and true cyclosis) are ordinary mechanical results de- 

 pending, in the first place, on the coalescence of adjoining pseu- 

 dopodia, and, in the second, on slight inequalities in the rates 

 at which the efferent and refluent streams of protoplasm are 

 moving (see Annals, November 1863, p. 332) — the granule 

 being, of course, borne along by the pseudopodium in which 

 that rate is the greatest, without any reference to its direction. 



Without embarking in a vain attempt to determine whether 

 the actions of the Rhizopods are dictated by instinct or are to be 

 regarded merely as tlie outward manifestations of a natural law 



