DR. HICKS, ON FRESH-WATER ALG, ETC. 5 
these forms in their life-history ; and also to rouse the atten- 
tion of Algologists to the unstable basis on which the genera 
of so many of these lower forms were resting. I am glad to 
find that, to a considerable extent, Mr. Archer agrees with 
the observations then made, though he appears yet to hold 
that there are some plants which can always be recognised by 
the eye, although it is difficult to convey the exact appear- 
ance by word or drawing. No doubt this is so; but yet it 
must be admitted as a very insecure basis on which to stand. 
A few points yet remain on which we differ, upon which 
I should wish to make a few remarks. 
Ist. Admitting that the disposition of the endochrome in a 
given cell, found at a certain time, is precisely the same as 
that in another found at another time, so that we all at 
once recognise it as identical in appearance, yet such con- 
stancy and similarity does not prove them to be the same 
species or genous, only that at a certain phase of their exist- 
ence they always assume the same appearance, and indeed, 
for anything we know to the contrary, unless observed very 
constantly and under other circumstances, they may have an 
essentially different origin. The arrangement of the endo- 
chrome is very variable, perhaps more so than any other 
feature, during the various periods of growth and division. 
Thus it becomes stellate in certain of the segmenting cells of 
gonidia of prasiola; in other stages it is quite homogeneous ; 
while in its lyngbya stage it is often with many vacuoles. 
But numberless examples can be quoted. 
2nd. Mr. Archer relies much on the shape of the cell to 
distinguish species; but here I must reiterate my remarks, 
and ask, if during the processes of growth and division, a 
single-celled plant is sometimes oval, at another round, as is 
undoubtedly to be found in the segmenting gonidia of the 
lichens and mosses, how can he hold it as more than a proof 
of its being in a certain stage of its life? With regard to the 
resemblance of certain cells, nothing could be more like the 
elongated oval cell of Palmoglea cylindrocyotis or Brebissonit 
than some of the segmentations of gonidia or cladonia. They 
were at the time I observed them merely smaller than the 
full size of the former. That they arose from cladonia was 
clear; yet, had it been found developing on the ground it 
would have been doubtless referred to Palmoglea Brebissonit. 
Now it must be admitted, either that the observations were 
erroneous, or that the Cladonia gonidium so resembled Palmo- 
glea Brebissonii as not to be capable of being distinguished ; 
at any rate, at that particular stage of their life. If the latter 
is accepted, then what proof have we of the separate exist- 
