460 ORIGINAL ARTICLES. 



Now on this I have to remark, in the first place, that the two 

 families Amcebina and Actinophryna, which are associated in the order 

 Proteena., differ essentially from each other in several particulars 

 which seem to me of great; physiological importance ; whilst I can- 

 not trace any such peculiar bond of union between them, as would 

 be required to justify their separation from all other Bhizopods and 

 their association into a separate order. Again: the foregoing arrange- 

 ment follows that of Prof. Miiller in dissociating Actinophryna from 

 Acanthometrina, to which they are much more nearly allied than they 

 are to Arnoebina. And thirdly, the ordinal separation of Gtromida 

 from Poramikceeea seems to me to be altogether unwarranted by 

 any essential difference, since the condition of the animal in these 

 two groups is in every respect the same ; while the diversity in the 

 material of the envelopes which they respectively form can no more 

 be admitted as a valid ground of separation in this group than in the 

 family Amcelina, of which Arcella exudes a chithious test like that of 

 Gromia, whilst Difflngia forms its test by the cementation of foreign 

 particles, as do several genera among Foraminifera. 



It is, as it seems to me, in the structural and physiological con- 

 ditions 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 at first sight 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, Amoela, Actinoplirys, and Gromia, — the sarcodc-bodics 

 of these three types presenting three distinct stages in the differen- 

 tiation of the protoplasmic substance of which they are composed, 

 and exhibiting, in virtue of that differentiation, three very distinct 

 modes of vital activity. 



I. — The lowest stage of this differentiation is seen in Gromia and 

 its allies, among which may be particularly specified a remarkable 

 naked form, which has been described by MM. Claparede and 

 Lachmann under the name of Lieberkuhnia, and which seems either 

 identical with the Pamphagus of the late Prof. Bailey (U.S.), or very 

 closely allied to it. In tins type the whole substance of the body and 

 of its pseudopodian extensions is composed of a homogeneous, semi- 

 fluid, granular protoplasm, the particles of which, when the animal is in 

 a state of activity, are continually performing a circulatory movement, 

 which has recently been likened by Prof. Schultze (and, as it seems to 

 me, with great justice) to the circulation of the particles in the proto- 

 plasmic network within the cell of a Tradescantia. The entire absence of 

 anything like a membranous envelope is evinced by the readiness with 

 Which the pseudopodian extensions fuse together whenever they come 

 into contact, and with which the principal branches subdivide into 

 finer and yet finer threads, by whose continual inosculations a net- 



