the Distinctive Characters in Amoeba. 127 



anterior and posterior portion of the body, but nevertheless 

 associated with a very high degree of true polymorphism. In 

 Astasia, on the other hand, we have a definite shape of the body 

 when at rest, but subject to variation when the creature is 

 moving. A. villosa may be regarded, therefore, as a link, if 

 need be. But the absence of a permanent aperture, either for 

 inception or excretion of food, defines its position at the head of 

 thfi Rhizopods ; whilst the permanent " buccal tube " of Astasia 

 marks that organism as belonging to a higher group. 



With reference to the "diaphane" or ectosarc, Mr. Carter 

 goes on to say, " This layer, as in other Amcehce, lies immediately 

 underneath the pellicula, and is distinguished from the sarcode 

 or endosarc within by its greater degree of transparency and 

 peculiar functions ; for while the sarcode is clouded and presents 

 a rotatorij motion, the diaphane is clear and distinctly endowed 

 with a locomotive and prehensile power. Analogij and actual 

 observation would lead us to infer that, in certain if not in all 

 instances, the ectosarc has the power of passing through [sic) 

 the pellicula by rupture of the latter — a fact which becomes 

 most evident when the pellicula is thick and resistant, as in 

 Amoeba hilimbosa, where it has been demonstrated by Auerbach, 

 especially in his third figure of this species (Siebold und Kolli- 

 ker's Zeitschr. vol. vii. p. 365, pi. 19. figs. 1-5, Dec. 1855)"* 



Before touching on the nature of the evidence on which the 

 existence of the ''pellicula" is based by Mr. Carter, I would 

 direct attention to what appear to me to be contradictory cha- 

 racters assigned to that portion of the structure, — namely, elas- 

 ticity so great as to enable it to yield a covering to the pseudo- 

 podia " almost to any extent,'^ and yet such an amount of 

 friability that "it admits of rupture (as in the introduction of 

 food) " ; for, since the pseudopodia are projected from the 

 "diaphane" (ectosarc), audit is also the "diaphane" "which 

 seizes the nutritious body, whether living or dead, animal or 

 plant, surrounds it, and encloses it" (Annals, July 1863, p. 35), 

 it is certainly difficult to conceive how the extreme elasticity 

 insisted upon in the case of the pseudopodia should be com- 

 pletely cast aside in the case of the food-particles. 



During my late survey of A. villosa, and after numerous care- 

 fully conducted examinations of the form usually known as A. 

 princeps (from quite distinct localities, and kept separately from 

 my specimens of ^. villosa), I can only say I have never detected 

 a trace of anything like a membranous outer investiture, except 

 in the single individual referred to in the May Number of the 

 ' Annals.' That specimen was in a state of nearly perfect quies- 

 cence, and apparently encysted ; and consequently my experience 

 * Ann. Nat. Hist. July 1863, pp. 31, 32 & 33. 



