ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
567 
spores of ScytosipJion lomentarius , similar to that recorded in the case 
of Edocarpus siliculosus , though by far the larger number come to rest 
without being impregnated. After conjugation the zygote rounds itself 
off, and contains two distinct chromatophores, each with an eye-spot. 
Division of the Nucleus in Spirogyra.* — After a review of the 
extensive literature of the subject, Herr L. Mitzkewitscli gives an account 
of his own observations on several species of Spirogyra, which differ in 
some important respects from those of previous observers, the species 
examined presenting no essential differences. The point which the 
author especially desired to clear up was the part played by the nucleoles 
in the division of the nucleus. In his description of the process of 
nuclear division, he agrees in important points with that of Strasburger 
and Tangl ; but in the role of the nucleoles he is rather in accordance 
with those observers who ascribe to them a more important function 
than that which belongs to the nucleoles in the higher plants. He 
especially insists on the part played by them in the formation of the 
nuclear disc. They do not disappear in the process of division ; and 
may be regarded as a concentration of the stainable substances of the 
nucleus. The nuclear disk stage in the karyokinetic process is remark- 
ably accentuated in Spirogyra. The material out of which it is formed 
is made up of two substances, chromatin in the form of roundish or 
elongated granules, coloured a bright red by safranin, each with a light- 
coloured border, and a second substance, possibly linin, coloured by 
safranin a light rose-colour. 
Conjugation of Binucleated Cells in Spirogyra. \ — By rapid cooling 
or the action of anaesthetics, Herr J. J. Gerassimoff obtained, in the 
division of the cells of Spirogyra majuscula , two cells, of which one con- 
tained no nucleus, the other either two of ordinary size, or one very 
large or compound nucleus. From these latter cells entire filaments 
were obtained by division, each cell of which contained either two nuclei, 
or one very large one ; these cells also increasing greatly in diameter. 
Germination of zygotes produced from these binucleated cells resulted 
in the production of filaments, the cells of which contained only one 
nucleus, but which were of abnormally large diameter. In the conjuga- 
tion of binucleated cells, parthenospores were sometimes observed. Two 
female conjugated with one male cell ; but the protoplasm of the latter 
coalesced only with that of one female cell, a partlienospore being formed 
in the other female cell. Double zygotes are apparently produced when 
two adjoining female cells are separated by an imperfect septum. 
Rhizoclonium4 — From the cultivation of two species of Bhizoelonium 
(B. hieroglyphicum and profundum) Dr. F. Brand comes to the conclusion 
that neither the relative length of the cells nor the formation of rhizoids 
is a trustworthy character for the separation of species, these characters 
being largely dependent on external conditions. Long-continued culti- 
vation gave no countenance to the view of a genetic connection between 
Bhizoelonium and CladopJiora. The formation of propagating organs of 
the nature of akinetes was confirmed. The following diagnosis of the 
genus is proposed : — Unbranched filamentous algte (or only with rudi- 
* Flora, lxxxv. (1898) pp. 81-124 (1 pi.). Of. this Journal, ante, p. 454. 
t Bull. Soc. Imp. Nat. Moscou, 1897 (1898) pp. 484-503 T9 figs.) (German). 
X Bot. Centralbl., lxxiv. (1898) pp. 193-202, 225-36 (1 pi.). 
