ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
63 
juvenescence of a single cell, accompanied by an increase in size; the 
simplest and a common type. (2) Two daughter-cells are produced from 
the protoplasm of a mother-cell, and from these arise two auxospores 
(. Achnanthes longipes , Rhabdonema arcuatum). (3) Two cells, lying side 
by side, cast off their old valves, and each grows into an auxospore, 
without any previous fusion or any visible interchange of contents ; 
much the most common type. (4) A true conjugation takes place ; the 
protoplasts of the two cells fuse together into one, and this grows into 
an auxospore ; also common. (5) Before conjugation the protoplasm of 
each of the two cells divides beforehand into two daughter-cells, and 
two auxospores are formed by the fusion of a daughter-cell from each 
mother-cell with the daughter-cell of the other one lying opposite to it 
( Amphora ovalis, Epithemia Argus, RJiopalodia gibbet, &c.). 
The process is then described in detail of the formation of two 
auxospores in Rhopalodia ( Epithemia ) gibba, which was found abun- 
dantly imbedded in the gelatinous envelope of Schizochlamys gelatinosa at 
PI on. The fixing of the cells during conjugation is assisted by peculiar 
gelatinous caps at their apices. Since the two nuclei which unite to 
form the nucleus of the auxospore are derived from two cells which have 
no near relationship to one another, the author regards the conjugation 
which results in its production as a true sexual process. 
Sporulation of Diatoms.* — Comte Abbe F. Castracane proposes to 
collect together all the recorded instances of the multiplication of 
diatoms by means of internal spores, and to found, on the variations in 
this mode of propagation, a new and more natural system of classification. 
He would classify e.g. the species of the present genus Synedra under 
two distinct genera, one terrestrial, the other marine, differing from one 
another in exhibiting an entirely different mode of sporulation. 
New Genera of Cyanophycese.f — Floating on the surface of a dark 
well, M. E. Roze found a gelatinous mucus, with very pale yellow spots, 
caused by an organism for which he constitutes a new genus of Chroo- 
coccacese Aplococcus, nearly allied to Aphanocapsa , and forming the 
lowest member of the family, with the following diagnosis: — Cellulae 
sphaericse, liberie, absque integumentis, in thallis mucosis homogeneis 
amorphis v. formge definitae nidulantes; cellularum divisio in unam 
solam directionem. The cells of A. natans sp. n. have a diameter of 
about 0*5 fx. They are largely attacked by a Micrococcus, probably 
undescribed, which appears to live on the gelatinous thallus of the 
Nostocaceee. 
From an adjacent well was obtained a filamentous organism, which 
becomes the type of another new genus of Cyanophyceae, Clonothrix , 
alied to Cladotlirix. C. fusca sp. n. is characterised by remarkable flask- 
shaped swellings of the branches. The diagnosis of the genus is as 
follows : — Trichomata elongata, articulata, simplicia v. pseudoramosa, 
plus minusve distincte vaginata; propagatio cellulis articulorum dis- 
junctis v. e medio fractarum vaginarum emergentibus ; generatio dubia, 
ampullis exiguis, apice evanescentibus, in quibus plasma fere hyalinum 
primo vacuolas deinde granulos paucos continet. 
* Atti Accad. Pont. Nuovi Lincei, xlix. (1896) pp. 107-13. 
f Journ. de Bot, (Morot), x. (1896) pp. 319—23, 325-30 (14 figs.). 
