of Foraminiferal Structure. 159 



measure attributable to the fundamental error which pervades 

 that classification of these organisms which has hitherto been 

 very generally, and in other respects very deservedly, held in 

 high estimation by naturalists. 



In an article upon the Systematic Arrangement of the 

 Rhizopoda, by Dr. W. B. Carpenter, published in the 

 'Natural-History Review' for October 1861, the author thus 

 expresses his views on the subject : — " It is, as it seems to me, 

 in the structural and 'physiological conditions of the animal 

 alone that we should, look for the characters on which our 

 primary subdivisions should be constituted ; and notwith- 

 standing that the extreme simplicity and apparent vagueness 

 of those conditions appear almost to forbid the attempt to 

 assign to them a differential value, yet a sufficiently careful 

 scrutiny will make it clear that, under their guidance, lines of 

 demarcation may be drawn as precise as in any other great 

 natural group, between three aggregations of forms which 

 assemble themselves round three well-known types, AmoBba, 

 Actinophrys, and Gromia, — the sarcode-bodies of these three 

 types presenting three distinct stages in the differentiation of 

 the protoplasmic substance of ivhich they are composed, and 

 exhibiting, in virtue of that differentiation, three very distinct 

 modes of vital activity " {loc. cit. p. 460). 



Regarding the perfect soundness of the principle laid down 

 in the opening sentence of the above extract, it may at once 

 be assumed that no question can arise. But this renders it 

 only the more inexplicable that such a thoroughly illogical 

 application of the principle should have followed as is in- 

 volved in the separation from each other, and the location in 

 three distinct ordinal divisions, of Amoeba, Actinophrys, and 

 Gromia — three forms in each of which are prominently com- 

 bined the only true structural characters of the animal that 

 clearly indicate an advance, in the highest group of Rhizopods, 

 towards the more complex organization of the Infusoria and 

 Gregarinse. 



The structural characters here referred to by me consist in 

 the possession, in common, by Amoeba, Actinophrys, and 

 Gromia, of a NUCLEUS and CONTEACTILE VESICLE: — the former 

 being the reproductive organ of the Rhizopod in its most fully 

 developed condition ; the latter, a fluid-respiratory organ, to be 

 met with, so far as my experience goes, for the first time in 

 the third or highest order of the Rhizopods *. On these 

 grounds I have done my utmost, for the last twelve years, to 

 prove that the three genera referred to cannot be thus parted 



* See Supplementary Note at the eud of these observations. 



