196 ARCHER, ON STEPHANOSPHERA PLUVIALIS. 
the Moss, of Volvox, we arrive at the vigorously, and actively 
and freely crawling, energetically and comparatively rapidly 
locomotive, amceboid bodies of Stephanosphera. We must 
regard, I think, the whole as manifestations of one and the 
same phenomenon—in the first lasting for a shorter period, 
and more feebly and slowly evinced; in the latter persisting 
for a longer period, and in the cases cited gradually more and 
more energetically and decidedly displayed, until (leaving 
the Myxogastres aside for the present), in the case of 
Stephanosphera this extraordinary condition seems to cul- 
minate. 
If this reasoning be correct, then, contractility, ameboid 
contractility-—for I can find no more comprehensive and ex- 
pressive single adjective term—must be accepted as an inhe- 
rent quality or characteristic, occasionally more or less 
vividly evinced, of the vegetable cell-contents, and this in 
common with the animal ; in other words, that the nature of 
the protoplasm in each is similar, as has indeed, as is well 
known, before been urged on grounds not so strong; thus 
reserving Siebold’s doctrine that this very contractility formed 
the strongest distinction between animals and plants, as he 
assumed it to be present in the former and absent in the 
latter of the two kingdoms of the organic world. Therefore 
an organism whose known structural affinities, and whose 
mode of growth and of ultimate fructification, point it out as 
truly a plant, but of which, however, certain cells may for a 
time assume a contractile, even a locomotive, quasi-rhizo- 
podous state, must not by any means on this latter account 
alone be assumed as even temporarily belonging to the animal 
kingdom, or as tending towards a mutation of its vegetable 
nature. And from this it of course follows that an organism 
whose structural affinities and reproduction are unknown, but 
which may possibly present an actively contractile, even 
locomotive, power, need not on this latter account be assumed 
as therefore necessarily an animal. In the former category 
fall the Volvocinacez and Rhizidium; in the latter category 
Euglena and its allies, the so-called Astasizean Infusoria, 
suggest themselves; and these must of course wait until 
their reproduction and history are better known before we 
can feel satisfied as to their true position, yet it seems highly 
probable that these will presently, if they do not even now, 
take their place amongst admitted plants. 
Several writers have indeed, from time to time, as is well 
known, put forward the (now, I think, generally accepted) 
view that the protoplasm of the vegetable and the sarcode of 
the animal cell are identical in nature; and, in seeking for 
