66 
Dii. WallicHj on the Polycystina. 
the sarcode^ and, in preference_, to avail myself of the more 
readily demonstrable and constant criterion of physiological 
as well as structural advance, afforded by the presence or ab- 
sence of one or both of the organs , on which my primary 
divisions of the Rhizopods are based. 
But although unprepared to regard the degrees of differen- 
tiation as applicable to the demarcation of Orders, ov, indeed, 
as affording perfectly constant characters under any circum- 
stances, there cannot be a doubt as to their affording, in the 
great majority of cases, a valuable means of completing our 
generic diagnosis. Beyond this their value does not appear 
to me to extend. And in support of this opinion I invite a 
comparison of the pseudopodial processes of the Foraminifera, 
Polycystinay Amoebina, and Actinophryna, as figured in the 
works of Schultze and Johannes Miiller already referred to — 
more particularly to the appearances presented by the Rota- 
lian, Milioline, and Textulariaii Foraminifera figured by the 
former observer — with some of the Polycystina figured by 
the latter, in order to show that between the pseudopodia 
of these two families which have been ranked in distinct 
Orders, principally on account of supposed differences in the 
disposition of the pseudopodia and the tendency of these pro- 
cesses to coalesce, if such differences were at all recognised, 
they have certainly not been sufiiciently depicted in the 
figures referred to. A comparison may also advantageously 
be instituted between the characters of the pseudopodia of 
Gromia and Lagynis, as exhibited in Schnitzels beautifully 
executed illustrations inasmuch as it will there be seen that 
whilst those characters are, in the case of Gromia Dujardiniij 
more Amoebanf than Actinophryan in type, those of G. 
oviformis are quite as Radiolarian in type as those of Lagynis, 
which, already very doubtfully placed by Carpenter amongst 
the Gromida,t is proved to belong to the Actinophryan and 
not to the Reticularian type, by the presence of a nucleus and 
a contractile vesicle, which the latter never exhibit. 
It will also be observed in Schnitzels work (pi. i, fig. 7) that 
the Actinophryan type of Lagynis is still more completely 
demonstrated by its being figured as presenting a nucleus. 
* ' Uber den Organismus der Polythalamien,' pi. i and vii. 
f See figure of Amceha porrecta^ as given in pi. vii, fig. 18, diadiAmceba 
villosa (Wall), 'Annals and Magazine of Natural History/ 1864. 
X Dr. Carpenter says, " It may be doubted whether this genus" (Lagy- 
nis), ** first discovered by Professor Schultze, .... should be ranked as an 
aberrant type of the family Oromida, or should be removed to the Actino- 
phryan group, the intermediate character of its pseudopodian extensions, 
and the strong resemblance of its test to that of Buglypha^ being such as to 
justify either position." — ' Introd. to Study of Foraminifera/ p. 65. 
