PALMELLACEiE. 
17 
development is very rapid, we may easily account for the rapidity with which the 
Protococcus nivalis has been seen to extend, and also for the vast surface covered by so 
minute an organism. Each individual is not more than toW of an inch in diameter, yet 
the surface of snow visibly reddened by the congregated masses often covers hundreds 
of square miles. A species very similar, if really different, called P. pluvialis , is found 
in shallow pools of rain water, on the surface of rocks, in gutters of houses, &c_ ; and 
has been noticed in very distant parts of the globe under various climatial conditions ; 
and of this species a most elaborate monograph illustrated by figures, has been given 
by De Flotow, in the Nov. Act. Leop. Carol. Nat. Cur. vol. 20, where no less than 
twenty-two distinct and many more subdistinct varieties, or rather states, are enume- 
rated, described, and measured to fourteen places of decimals (!) and figured. Several of 
these forms are endowed with movements resembling those of the infusorial animalcules, 
and have been described as animalcules by Shuttleworth in his account of the Bed Snow 
(Bib. Univ. Geneva , Feb. 1840.) 
A little higher in organisation than Protococcus is the genus Gloeocapsa ( Hcemato - 
coccus) in which what is only a passing phase of the Protococcus becomes a permanent 
character. In this we have several cells (of the structure of Protococcus ) enclosed 
within a common, primary cell, which is persistent, or at least partially so. In some 
species (as in G. Hoolceri) the primary cell-coat exfoliates repeatedly, the old coats 
remaining permanently attached on one side to each other, and to the cell, which per- 
petually bursts through them ; and thus a sort of spurious frond, simple or branching, 
is formed, consisting of exuviae, each branch being tipped with the living cell, which 
shines like a gem at its summit. These plants occur generally in damp situations, on 
rocks and among mosses, about the spray of cascades, &c., and Kiitzing has described 
and figured upwards of fifty. 
Next come the Palmellce proper, where a large number of protocOccoid cells are enclosed 
within a common gelatine, in which they sometimes appear to be distributed without 
order ; and sometimes arranged in a subquaternary manner. In this latter case the 
structure approaches very closely to that of Tetraspora, a genus we have already 
referred to the TJlvacece ; but which is placed by many authors next to Palmella. 
Possibly among these obscure plants forms are associated in one genus which will be 
separated when their development is better understood. Among some of the Palmellce 
Broome and Thwaites have described and figured a more definite organization than was 
previously known ; namely, that the apparently scattered cells of the mass are connected 
in an early stage of growth, by means of slender gelatinous threads, with a central cell 
* This extraordinary essay is well worth looking at — (I will not say carefully perusing) — as one of the most 
remarkable commentaries on the text, “ how great a flame a little fire kindleth.” The object to be examined 
is a microscopic Alga of the simplest possible structure, being in fact merely an isolated living cell. All that 
need to be said of its history might, one would suppose, easily have been written in a page or two. But the 
learned and most laborious author has occupied nearly two hundred large quarto pages on this theme ; and 
not content therewith, has appended long tables of decimal measurements of microscopic areas and volumes, 
whose only reference to his subject appears to be that they enable him to arrive at such important calculations 
and useful results as describing the mean differences of the shorter and longer diameters of different individuals 
of his Protococcus, and their mean comparative bulk and spherical aberration. In computing these tables, the 
decimals have been carried sometimes to fourteen places, and in most cases at least to six. 
