8 BARKAS, ON DIATOMACEZ. 
it may take the position Mr. Archer and others have 
assigned it. 
At present, on the other hand, we know that the contents 
of cells fuse readily under certain circumstances ; and other 
cases may some day be found which may solve the question 
where this process and antheridia are plainly found. For 
supposing it was ultimately found that Spirogyra has Anthe- 
rozoids, then we must agree that conjugation is nothing more 
than a vegetative process. This hitherto has not been 
noticed; but we are hardly in a position to say that it will 
never be so. Till then we shall, I conceive, advance quicker 
if we do not assign conjugation a too definite position. 
Finally, Mr. Archer asks, “‘ Can a phenomenon which has 
been going on for years and years uncountable, be simply 
accidental, and devoid of significance?” ‘This question is 
scarcely pertinent, because I have never said it was a simple 
chance occurence, but have placed it with other vegetative 
processes, such as segmentation, &c. As to the antiquity of 
the process the same of course may be said of ordinary 
growth or cell-division. That conjugation restores the vigour 
of the plant enfeebled by frequent division can scarcely be 
doubted, and that it is of much value in its life. I do not for 
a moment deny, but I do not think that we are yet warranted 
in employing it as a test of generic or specific distinction, 
because it is very doubtful whether it is an evidence of the 
perfectness of the cells in which it occurs, and because we 
are still ignorant to what extent it may be found in the lower 
tribes ; nor are we yet sure that plants, which we know show 
it most distinctly, have not at some period of their life the 
true antherozoids. 
On PrevRosigMa, Donx1n1A, ToxonipEA, and AMPHt- 
prora. By T. P. Barxas, Newcastle-on-Tyne. 
(Read before the Tyneside Naturalists’ Field Club, February 8th, 1866.) 
Ir is my intention this evening to direct the attention of 
the members of the club to four closely allied genera of 
diatomaceze which have recently been found on that part of 
the Northumberland coast which is in close contiguity to the 
Mouth of the Tyne. Two of the genera are well known to 
microscopists ; one has only recently been discovered and 
named by Dr. Donkin, and the other, which was discovered 
