222 ARCHER, ON CYLINDROCYSTIS, 
Micrasterias (I do not, I need hardly say, restrict myself to 
that genus, but rather mention it as an example) has yet to 
be demonstrated. I venture likewise as yet to hold that the 
admission of some forms as species, and others not less well 
marked as varieties, in this family (I do not now, of course, 
refer to Protophyta in general), is, on the whole, altogether 
arbitrary; and I for one cannot refuse to go the length that 
Nature seems to me here to go, and admit as species all 
those ultimate forms which seem to be constantly distinct, 
keeping their ultimate characters to themselves; and each of 
which, by its own idiosyncrasies, one can at a glance perceive 
is the very same identical plant which, described or unde- 
scribed, one encounters more or less rarely or frequently in 
its own suitable localities. 
It will thus be seen, while I venture very deferentially, 
and with the highest respect, to differ on points in relation 
to some Protophyta from Dr. Hicks and Dr. Wallich, that 
there are others on which I cannot but agree as yet with 
both observers. Nor does it seem to me that the views here 
put forward conflict with those I ventured to express in my 
paper read to the Society last session, on an ameeboid state 
of Stephanosphera, as regards the, perhaps in individual 
opinion, debateable but, as I still hold, by no means actually 
convertible, lower forms of animal and vegetable life. 
Because some organisms are not always what they seem to 
be, inasmuch as, in the course of their development, they 
may submit themselves to several apparently more or less 
diversified phases, whilst others (as our Mesotzenium and 
Cylindrocystis) seem to be in this respect more restricted, is 
not, I think, in either case an argument that Protophyta, or 
even some Palmellaceze, may not be subject to specific limits, 
not to speak of a change from one kingdom to another. 
With Dr. Hicks I must, indeed, wholly coincide, that in the 
study of the Protophyta it is especially desirable that the 
history of each be, as far as possible, made out, in order to 
discover the mature forms, and to trace out the seeming 
changes through which they may pass; but is not this, after 
all, in other words, to endeavour to find out what are the 
species and their limits, and to learn to discriminate between 
them? But assuredly, were all this known, many spurious 
“ species ” would have to be erased, at least among certain 
types. But, whatever phases they may run through, they at 
least must revert eventually to the parent or type-form ; for 
the same forms turn up and vanish again and again, and 
season after season, each in its own kind of situation or 
habitat; and it seems more reasonable that we should sup- 
