ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
233 
liquefy gelatin, though more slowly than bacteria. The effect of this 
and other similar organisms on other nutrient substances is described in 
detail. Chlorella the author regards as belonging to the Pleurococcacese, 
and as presenting the lowest form from which the green algae are derived ; 
it belongs to the same type as Eremosphsera. Its identity was again 
demonstrated with the Zoochlorellee of Hydra viridis, the green variety 
of Stentor polymorphous, Paramecium aurelia, and Spongilla fiuvia.tilis ; 
but the author’s observations tend to show that J Raphidium and Scene- 
desmus are perfectly distinct organisms from these. The genus Chlorella 
is defined as consisting of unicellular green algae, with spherical, 
elliptical, or flattened cells, from 1-6 p in diameter, usually with only 
one chromatophore, and no or only an inconspicuous pyrenoid ; usually 
only one nucleus, or sometimes two, consisting only of chromatin ; 
multiplication by free cell-formation from successive bipartitions ; 
zoospores altogether wanting. It occurs in both fresh and salt water, 
and probably also on the soil. Four species are described : — C. vulgaris 
(Chlorococcum protogenitum Rbh.), C. infusiouum ( Chlorococcum infusionum 
Ebh.), C. ( Zoochlorella ) parasitica Brandt, and C. ( Zoochlorella ) con- 
ductrix Brandt. 
Another form produced under similar circumstances is Chorosphoera 
limicola, which differs from those already described in readily producing 
zoospores; it bears a strong resemblance to Chlamydomonas pulvisculus 
in its structure and mode of life. 
The gonids of the lichen Physcia parietina are identical with Cysto- 
coccus humicola Nag. They multiply by a series of bipartitions, or, 
under certain circumstances, produce zoospores closely resembling those 
of Chlorosphsera ; no conjugation between these was observed. 
Diplocolon and Nostoc.* — Pursuing his investigations on the meta- 
morphoses which Scytonema clavatum undergoes when grown on a nidus 
of Hepaticse, Herr H. Zukal found that filaments, when moistened after 
being accidentally desiccated, had become, as well as their enveloping 
sheath, distinctly shorter and thicker. These filaments eventually 
passed over entirely into the NosZoc-condition ; or the trichomes became 
enveloped in thick yellow secondary sheaths, very often consisting of 
two distinct layers, and coiled in a loop-like fashion. In this con- 
dition they agree altogether with the characters of Diplocolon, which 
must be regarded as a condition of development connecting Scytonema 
with Nostoc. The D«pZocoZow-filaments finally passed over into Nostoc 
microscopicum. 
Oscillariaceae.f — M. M. Gomont gives a revision of the genera of 
the Homocystous Nostocacese (Oscillariacese) founded on the same 
principles as that of Bornet and Flahault for the Heterocystous Nosto- 
cacese, | and based on an examination of living and dried specimens, and 
of published descriptions. In accordance with these writers he uses the 
term trichome for the string of cells, wad filament for the filament inclosed 
in its sheath, and proposes cap (coiffe) for the thickening often produced 
in the upper part of the membrane of the apical cell, and furnishing an 
* Notarisia, v. (1890) pp. 1106-15 (1 pi.). Cf. this Journal, 1890, p. 222. 
t Journ. de Bot. (Morot), iv. (1890) pp. 349-57. 
X Cf. this Journal, 1890, p. 103. 
