126 Dr. G. C. Wallich on the Value of 



on the application of iodine, the margin becomes of a deep violet 

 colour, while all the other parts of the Rhizopod exhibit nothing 

 but a more or less deep amber tint, seems to confirm it by che- 

 mical differentiation." Again, " Such a covering has been de- 

 monstrated by Auerbach in^. hilimhosa, and more satisfactorily, 

 on account, probably, of the pellicula in this species being more 

 rigid ; but Auerbach does not show that it is coloured by iodine, 

 although he figures starch-globules thus turned blue within it.^^ 

 . . . . " We must also infer that it is possessed of great elasticity 

 and tenacity, so that it can yield a covering to the pseudopodia 

 almost to any extent (as proved by the actinophorous rays of 

 those Rhizopods which infest the cells of plants remaining after 

 the sarcode has withdrawn itself into an interior or secondary 

 cell) ; also that it admits of rupture (as in the introduction of 

 food into the sarcode), and yet can heal over rapidly again. 

 Thus it can undergo comparatively unlimited extension even to 

 discontinuity, but possesses no adhesiveness externally, as evi- 

 denced by nothing adhering to it which is not seized and kept 

 there by the instinct of the animal. Furthermoi'e, in A. princeps 

 the pellicula is allied to the cell-wall of plants by position, 

 and, from chemical evidence {i. e. when treated with iodine), 

 by an amylaceous composition." (Annals, July 1863, p. 32.) 



In referring to the analogous organs of Amceba and Serpicula 

 verticillata, Mr. Carter goes so far as to say, " The difference 

 between cellulose and pellicula, and the absence of the vesicula, 

 &c., are points which have so little [!] to do with the analogy in 

 question when the latter is followed up through Astasia, Euglena, 

 Navicula, Closterium, &c., into (Edogonium and Nitella, to Serpi- 

 cula, that very little doubt will, I think, then remain of the 

 offices of the nucleus in Amceba being similar to those of the 

 nucleus of the plant-cell, whatever these may hereafter prove to 

 be" (Annals, ser. 2. vol. xviii. p. 223), thus instituting a com- 

 parison between the plant-cell and a portion of the Amoeban 

 structure regarded by him as typical, but of which not a trace 

 has ever yet been seen except in A. hilimbosa or the encysted 

 state of other species, and then making this comparison a basis 

 for assuming the identity in function of an organ which is pre- 

 sent in the plant-cell as well as in Amoeba. 



It appears to me that an error of a serious nature is com- 

 mitted in associating the Rhizopods, whose bodies are poly- 

 morphous, with the Infusoria, whose bodies are monomorphous. 

 Mr. Carter speaks of Astasia and Euglena as " freshwater Rhizo- 

 pods " (Annals, ser. 2. vol. xviii. p. 227). But even here, I think, 

 the distinction about to be drawn holds good, independently of 

 differences in internal organization. In Amceba villosa we have 

 a determinate indication, in a non-testaceous Rhizopod, of an 



