254 HICKS, ON MR. ARCHER’S PAPER ON ALGA. 
with another new species, he thinks is referable rather to 
another genus, it would seem almost a hopeless task to assist 
in the work. If Kiitzing, Naegele, De Bary, and other 
equally celebrated algologists, are unable to decide the position 
of the various Palmellacez, and are further unable to agree 
upon what are the essential characters by which to settle these 
points, what can be better proof of the intrinsic difficulty of 
the whole question? If by one observer the envelope of 
mucoid matter be taken as a specific or even generic sign— 
if the mode of segmentation be taken by another as of specific 
or generic value—if the size of the cell, or the position of the 
nucleus, or the mode of diffusion of the endochrome within 
the cell, be sufficient in the eyes of another to separate genera— 
if, as Mr. Archer contends, the oval shape is another impor- 
tant distinction—it seems to me no wonder that the difficulty, 
acknowledged by all, has arisen. 
If, again, inability after careful research to determine what 
is meant by Kiitzing’s character of the genus Palmogleea be 
admitted by Mr. Archer and Braun; and if Mr. Archer thinks 
that this genus is separable into five types, two of which he 
thinks do not at all belong to it; when, in fact, no one 
algologist can tell distinctly what is a Palmogleea, so as to be 
understood by any other algologist ; then, I must confess, it 
seems difficult to understand how Mr. Archer can find suffi- 
cient ground to state that a Macrococca is not the state 
figured by me as similar to Palmogloea amongst the forms 
produced by the lichen-gonidia. Mr. Archer is by no means 
certain of what I mean by Palmoglea Brébissonu, for he 
questions whether it be the same as that which Kiitzing makes 
identical with Palmella cylindrospora, which Ralf considers 
identical with Penium Brébissonii, and which Mr. Archer 
places with Cylindrocystis; and which, as far as can be 
ascertained, Mr. Thwaites calls Coccochloris Brébissonii, 
although Mr. Archer thinks he means the Trichodictyon 
rupestro. The exact characters of this form, it will thus be 
seen, are by no means settled by any one of these observers. 
The exceeding confusion prevailing in this species extends 
similarly throughout the whole group, and leaves it in such 
a state of uncertainty that it would be well if the whole of 
these forms were to undergo complete remodelling. 
But the question first of all arises, how is a single cell to be 
distinguished from another single cell? What reliable charac- 
ters are to be fixed upon which can be considered as of generic 
value? When we consider through what various forms those 
cells pass whose life-history has been carefully watched, as 
for example, Protococcus pluvialis, the very species with 
