DUBLIN UNIVERSITY ZOOLOGICAL AND BOTANICAL ASSOCIATION. 241 
occurs, and this more especially (in which my own experience confirms 
Mr. Halts’), in specimens which have been kept some time in the house. 
These minute moving bodies are apparently formed of the cell-contents 
disintegrated and subdivided into an immense number of granular par¬ 
ticles, and which exert an active, vigorous, tremulous, dancing kind of 
motion, as if each one were elastic and perpetually meeting with some¬ 
thing to make it rebound, and as quickly stopped only to meet with ano¬ 
ther impulse, resulting in little or no actual change of position of the in¬ 
dividual particles, notwithstanding all the commotion. I greatly fear this 
fanciful description will hardly be intelligible; indeed I think this peculiar 
phenomenon thus attempted to he described must be witnessed to be com¬ 
prehended. These moving granules have been assumed to be zoospores, 
but the phenomenon may be due, possibly, to some sort of “ molecular 
motion.” I have myself seen it in numerous genera and species. Mr. Ealfs 
suggested that they (the agitated granules) are zoospores, and says they 
occur when the cell approaches maturity. Dr. Carpenter calls them such, 
and says they may be ciliated; but without giving authorities. I have 
seen this curious movement in cells undergoing division, and as active 
in the young and as yet unformed segment of a frond during division 
as in an old fully developed one. I have noticed, too, a precisely similar 
movement in the germinating spore of an (Edogonium. To my eyes this 
u swarming motion” does not resemble that of the true zoospores of 
Cladophora, or of other Algas which give birth to undoubted zoospores. 
1 have not seen anything to indicate cilia, with only a “inch object- 
glass, however; and for my own share I believe the nature or import 
of this curious motion is undecided, and I should be glad, indeed, to 
meet with any observations which would throw light on this phenome¬ 
non, while, upon this point, as on many others, it would be as untrue, 
as it would be unbecoming, to avow myself as not open to conviction. 
I have before stated that the Desmidiacese were formerly regarded 
as animals. The principal reasons advanced by the Ehrenbergian school 
for surrendering this group to the zoologist, are, that they exert a volun¬ 
tary motion; that they increase by transverse self-division; and that 
in Closterium there are at the extremities apertures and protruding 
organs continually in motion. With regard to the first reason, it is clear 
that using the term “ voluntary” is a begging of the question. That 
they move is beyond doubt, for these organisms, if buried in the mud, 
will come to the surface and become exposed to the light. While this 
is doubtless a highly curious phenomenon, it strikes me as not more 
remarkable than any flowering plant cultivated in-doors bending its 
leaves towards the window under the stimulus of light (not to speak of 
the vigorous movements of unquestionable plants high in the scale). As 
to the second reason, the increase by transverse self-division,—this is 
by no means an exclusively animal characteristic; the very same argu¬ 
ment might, with greater force, be applied in proof of their vegetable 
nature, as I need hardly insist on. With regard to the third reason,— 
the various species of Closterium have been too often made the subject 
of examination by numerous observers to allow of terminal apertures 
