HICKS, ON MR. ARCHER’S PAPER ON ALGA. 255 
which Mr. Archer illustrated his paper, how are we to tell to 
what genus any single cell belongs? how can we tell whether 
it be a fixed form, a separate entity, or merely a transitional 
form of some other growth? When, again, we find, as I have 
shown in this Journal, and in the ‘ Transactions of the Linnean 
Society,’ that cells quite similar in all respects are produced 
during the segmentation of the gonidia of the lichens, mosses, 
Lycopodia, Prasiola, &c., in what manner, may it be asked, 
are we to tell to what group it belongs, and how can we say 
that it is certainly a separate Palmellaceous plant ? 
It is clear that the whole question must be gone over com- 
pletely, not with the distinct intent of dividing each of these 
forms into genera and species, but for the purpose of tracing 
their history as far as practicable, in order to find out through 
what various forms they can pass, and more especially to in- 
quire how many homomorphous forms can spring from 
different structures. 
The whole case resolves itself into this heavy task, a subject 
which will require the combined efforts of many observers, 
and one which I am fully aware will hold out little attraction 
for those whose love of distinctness and definiteness draws 
them rather to analysis than to synthesis. It is one to which, 
if Mr. Archer will apply his patient and careful habits of 
observation, he will find it repay his pains far more amply 
than endeavouring to unravel the confusion of authors. These 
views I have already expressed in the papers above quoted, 
and I may repeat that I consider that, till the life-history is 
traced out, it is impossible to tell whether the growth before 
one be a distinct form or not. 
The principal point which must be first determined is, 
what are the characters to the differences of which we can 
assign a generic or specific value? Is size to be taken as a 
guide? The size of any cell depends on many circumstances, 
as, for instance, upon the rate of segmentation compared with 
individual growth. This is well seen by observing continu- 
ously the process of the gonidia of lichens or mosses. The 
size depends also upon the temperature and other external 
circumstances affecting the activity of its vital powers. There 
* is no doubt the subdivision of a cell may extend to almost 
an invisible point, and in that state it may so remain for an 
indefinite period ; and that it may begin at any time to grow, 
till it reach the size of the parent, and probably to a still 
larger, provided, however, segmentation does not commence. 
Does the position of the nucleus help us? How, then, can 
those states be classified in which there is no nucleus? I 
think few will consider that the position of the nucleus, of a 
