ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 029 
Abnormal Conjugation in Spirogyra.* * * § — Mr. R. A. Robertson finds, 
in an undetermined species of Sjpirogyra , that conjugation may occur 
between one male and two female cells, while that between one male and 
several female filaments is very common. No distinction could be de- 
tected in the diameter of the filament or in the size of the cells between 
male and female filaments. In some cases a zygospore was found 
stretching from one cell to another through the conjugating tube. 
Variation in Desmids.f — In an exhaustive paper on this subject, 
Mr. G. S. West shows that the Desmidieae are morphologically specialised, 
and exhibit a marked pattern and symmetry of form, major and minor 
symmetries being recognisable in many species. A summary is given of 
all that is at present known concerning the variation in the cell-contents 
and in conjugation, and reference is made to the variability of the pyre- 
noids and to the moving corpuscles in Closterium. The author’s con- 
clusions may be summed up as follows : — 
(1) The structure of the cell-contents is one of the most constant 
features exhibited by a species, but is one of little value in classification. 
(2) The outward form of the cell, as seen in front view, varies within 
certain limits which are usually very small, but which may in excep- 
tional cases be considerable. The form of the vertical view is, as a rule, 
a more constant feature than the form of the front view. (3) The orna- 
mentation of the cell-wall is relatively constant, being always arranged 
according to a definite law, which is only transgressed by variations in 
one or more of the individual component groups which constitute the 
pattern of arrangement. (4) The prolific growth and rapid division of 
immense numbers of desmids have a tendency to produce variations from 
the typical forms. (5) Slight changes in the conditions of environment 
cannot affect the characters of a species unless they act for long periods 
of time. 
Glceoplax, a new Genus of Chsetophoraceae.J — Among a number of 
Algae from the elevated moors of Prussia, Herr W. Schmidle describes, 
under the name of Gloeoplax Weberi g. et sp. n., one which forms soft 
expanded hyaline unilamellar discs on the surface of Sphagnum-le&ves , 
in which are imbedded cells containing chlorophyll ; filaments are put 
out from the margin of older plants. The green cells contain one or 
more parietal chlorophyll-discs, small starch-grains, a nucleus, but no 
pyrenoid. Swarmspores are formed in the round erect cells of mature 
plants, one in each cell. They develope into filaments of loosely attached 
cells imbedded in mucilage. From the absence of pyrenoids the author 
concludes that Glceoplax is not a palmella-condition of Stigeocloniam , 
Chsetophora , or any allied genus. The young cells are about 5 p in 
diameter, and 2-4 times as long as broad ; older cells round, and 8-10 /x 
in diameter. 
Fossil Dasycladaceae.§ — Herr G. Steinmann describes a number of 
fossil algae belonging to this family, from the upper Cretaceous series 
* Trans. Bot. Soc. Edinburgh, xxi. (1899) pp. 185-91 (2 pis.). Cf. this Journal, 
ante, p. 418. 
t Joum. Linn. Soc. (Bot.), xxxiv. (1899) pp. 366-416 (4 pis. and 4 figs.). 
t Hedwigia, xxxviii. (1899) pp. 159-62 (5 figs.). 
§ Bot. Ztg., lvii. (1899) l te Abt., pp. 137-54 (21 figs.). 
