ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
GC9 
Protophyta. 
a. Schizophyceae. 
Development of Eremosphsera.* — Prof. R. Chodat lias followed out 
the life-history of Eremosplisera viridis , which has no relationship to the 
zygospores of desmids. In its mature condition the cell divides in the 
ordinary manner of the Protococcoideae ; and it may then pass into a 
Palmella or Glceocyslis state by swelling of the membrane; or the two 
cells may again divide into four, the cell becoming thus a sporange. The 
zoospores are produced from the Palmella- form, and resemble those of 
Chlamydomonas. Eremosplieera must be placed provisionally among the 
Protococcacese, but shows a distinct affinity to the Yolvocineae. 
Terminology of Diatoms.f — Dr. 0 . Muller proposes a new termi- 
nology for diatoms, founded, in its main points, on the scheme of Schulze % 
for animals. 
The overlapping half-cell is the epitheca, the underlapping half-cell 
the hypothecs ; the shells are valves, and for the girdle-bands he 
proposes the term pleurse ; the epitheca is composed of the epivalve or 
larger shell and the epipleura , the hypotheca of the hypovalve or smaller 
shell and the liypopleura ; between the shells and the girdle-bands are 
often other pieces of cell-wall, the intermediate bands or copulse. 
Although the epitheca and hypotheca are unequal, they are yet similar ; 
to this resemblance the term consimilitude is applied. Diatoms are 
either “ syngrammse ” with linear, or “ sympedse ” with superficial 
symmetry. The main axis is always “ heteropolar,” with two or more 
“ isopolar ” transverse axes, vertical to the main axis. If the transverse 
axes are equal the cell is monaxon ; if unlike, it is heteraxon. The main 
longitudinal axis of the diatom is the pervalvar axis, viz. the line which, 
from the centre of the dividing plane, penetrates the cell-cavity in the 
epithecal and hypothecal directions, at equal distances from homologous 
points of the enclosing walls, and unites the centres of the two valves. 
In all diatoms this axis is heteropolar ; in the syngrammal forms it is 
also the line to which all parts of the cell lie symmetrically ; its middle 
point is the “ centre.” In the monaxou syngrammee the plane which 
contains the pervalvar axis is the “ meridian ” ; the planes parallel to it 
are “ parameridian.” The plane which passes through the centre 
vertically to the pervalvar axis is the “ transversan ” plane ; those 
parallel to it are “ paratransversan.” The axis which lies in the trans- 
versan plane, cutting the pervalvar axis, is the “ transversal ” axis. The 
apical axis is the line which passes through the centre of the pervalvar 
axis in the direction of the raphe, at equal distances from homologous 
points of the girdle-band surfaces, and through the apices. The second 
transversal axis at right angles to the apical one, and passing through 
the centre of the pervalvar axis, is the transapical axis. The plane 
which passes through the apical and the transapical axes is the valvar 
plane ; the plane at right-angles to this one passing through the pervalvar 
and the apical axes is the apical plane ; the one at right-angles to both. 
* Bot. Ztg., liii. (1895) l te Abt., pp. 137-42 (L pi.), 
t Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 222-34 (1 pi.). 
t Cf. this Journal, 1893, pp. 159, 815, 816. 
