Archer — On Freshwater Rhizopoda. 
69 
that not only are the indiyidual ' species,' in certain types or genera, to 
a great extent invalid, but would even combine together certain recog- 
nised distinct genera as hardly correctly or actually distinguishable 
individual forms. As regards Difflugise, the view propounded by Dr. 
Wallich seems to be endorsed by Mr. H. E. Brady, that the differences 
hese present are due but to the influence of external circumstances. 
But I venture to think that such a view is untenable, when, time 
after time, and season after season, in pools very many miles asunder, 
or in a familiar single pool, with exactly the same crude materials 
around, exactly the same substances in suspension or solution in the 
water, exactly the same kinds of food accessible, and (so far as we can 
observe) exactly the same influences in action, such as regard light, 
&c., current or stillness of the water, or such like mechanical or phy- 
sical circumstances — when, I say, under all these precisely similar con- 
ditions we constantly find associated and maintaining their specialities, 
it may be in one and the same drop of water, a more or less considerable 
number of forms with more or less mutual affinity, representing it may 
be several recognized distinct genera, or even families. 
There is a little mass of sarcode" side by side with several other 
little masses of '^sarcode," all very like one another, each of which 
somehow contrives to build an edifice in which to dwell. An abun- 
dant quantity of different and various materials abounds around. Some 
choose long diatoms, others short; some choose sandy particles or other 
materials. One form constantly contrives to attach its materials in the 
roughest and most slovenly" manner. Is it with a view to the gro- 
tesque, or the picturesque, or what ? Another form as constantly im- 
pacts its building materials with a mosaic evenness and regularity. 
Is it with a view to turn itself out elegant and spruce ? Another 
form constantly sticks on its materials, externally, so loosely as hardly 
to deserve to gain credit for any architectural capacity. Is it due to in- 
herent laziness of disposition ? Another form wants no such extraneous 
assistance ; its inherent nature admits of a test sufficiently strong being 
secreted in its own structural development. There are, then, various 
sarcode " bodies capable each of making such choice from a common 
stock of materials, each capable of applying those materials in its 
own way, whilst to me these and such like specialities seem to be 
bound up with a considerable amount of constancy in outward figure, 
and a certain amount of constancy, also, in dimensions, which are more 
than accidental. Again, there is sarcode" capable of secreting solid 
'^skeletons" of various types and forms; and, side by side with it, other 
sarcode" not capable of this, the external circumstances being alike. 
There is ''sarcode" which makes its ''skeleton" a hollow globular 
fenestrate structure finally external to its own living mass ; and, side by 
side with it, other "sarcode" which makes its skeleton separate por- 
* H. B, Brady, " Analysis and Descriptions of the Foraminifera," in the Ann. 
Nat. Hist., October, 1870, p. 273. 
