638 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
decisive on the question of the genetic connection of this organism with 
Pleurococcus vulgaris. 
Dictyosphaerium.* — Mr. G. Massee has followed out the life-history 
of Dictyosphserium Ehrenbergianum. In its earliest stage it cannot be 
distinguished from a small specimen of Pleurococcus vulgaris. After 
considerably increasing in size the spherical cell divides simultaneously 
into four equal parts. The mucilaginous portion of the mother-cell- 
w r all does not divide along with the chlorophyllous portion, but con- 
tinues to increase in quantity, and envelopes the segments in a con- 
tinuous hyaline stratum. The segments of the mother-cell eventually 
become spherical, and still remain attached by their central stalk-like 
portions, which are hollow, the contents of the minute cavity being 
sometimes coloured green ; the cavity subsequently becomes completely 
obliterated. Each of the four segments again divides into four by a 
double bipartition ; and this process may again be repeated once or 
twice. The contents of each final division escape as a zoospore, pro- 
vided with two very long and slender cilia. 
Movements of Diatoms. — Mr. C. Onderdonkf finds that several 
species of Pinnularia and one of Nitzschia , when in active motion, are 
at once arrested by a delicate application of methyl-anilin-green ; this 
stains blue a mantle of protoplasm, which it raises up from the surface 
of the frustule, and shows, by the varying depths of colour, that it is 
folded and wrinkled ; the contents of the diatom itself are stained green. 
He concludes from this that the motions of diatoms are due to an 
excessively thin external coating of protoplasm, which is probably not 
more than 0*00002 in. in thickness, and in a state of perpetual pulsation 
as long as the cell is in a living state. 
Mr. E. W. Haskins,J on the other hand, believes, from observations 
on a species of Nitzschia , that the motion is due to the action of very 
minute cilia. 
Schizomycetes. 
Classification of Bacteria.§ — Sig. Al. Messea suggests that the 
presence or absence of cilia in Bacteria may afford a basis for classifica- 
tion, and gives the following scheme : — I. Gymnobacteria ; II. Tricho- 
bacteria. 1, Monotricha ; 2, Lophotricha ; 3, Amphitricha ; 4, Peritricha. 
The Monotricha possess a flagellum at each pole, e. g. B. pyocyaneus. 
Lophotricha are characterized by a tuft of flagella at one pole, e. g. 
Bacillus of blue milk. The Amphitricha have one cilium at each pole 
( Spirillum volutans). The Peritricha have flagella all round ( Bacillus 
proteus vulgaris , B. typhosus). 
Plasmolysis in Bacteria. || — Plasmolysis, says Herr A. Fischer, is 
that phenomenon occurring in the protoplasm of vegetable cells under 
the influence of substances having affinity for water, such as saline 
* Journ. Linn. Soc. (Bot.), xx7ii. (1891) pp. 457-62 (1 pi.). 
t The Microscope, x. (1890) pp. 225-30. X J om ' cit., PP* 272-3. 
§ Rivista d’ Igiene e Sanita pubblica, i., No. 14. See Centralbl. f. Bakteriol. u. 
Parasitenk., ix. (1891) pp. 106-7. 
1| Berichte lib. d. Verhandlungen Sachs. Gesell. Wiss. zu Leipzig, i. (1891) 
pp. 52-74 (l pi.). 
