ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
239 
host-plants, which arc not interchangeable, viz. respectively on Allium 
ursinum, Arum maculatum, Convallaria majalis, and Bhamnus Frangula. 
Herr W. Tranzschel * * * § identifies Cseoma inter stitiale, parasitic on 
Bubus saxatilis , with Puccinia Peclciana, found on various species of 
Bubus, which must now be known as P. inter stitialis. 
Achromatium oxaliferum.f — Herr W. Schewiakoff describes an 
organism which he designates Achromatium oxaliferum. It was obtained 
from the mud of the Altrhein aud appears to have a wide distribution. 
In shape it is elliptical to spherical, and occasionally exhibits slow 
intermitting movements, but no locomotive organs were observed. Some 
examples were imbedded in a gelatinous sheath. The membrane of 
Achromatium has a honeycombed structure and a proteid composition. 
Within the meshes of this honeycomb structure are peculiar highly re- 
fractive corpuscles which in the living organism render the central body 
quite invisible. From their chemical and optical reactions the author 
concluded that these corpuscles are composed of oxalate of lime, and 
considers that they are analogues of chromatin corpuscles. The fission 
stage of the organism is marked by a constriction about the centre ; by 
the gradual deepening of this constriction the organism finally separates 
into two equal halves. 
Protophyta. 
a. Schizophyceae. 
Structure and Cell-division of Diatoms.^ — Herr E. Lauterborn has 
detected an actual perforation in the wall of a species of Surirella, at the 
spot where foreign bodies become attached and are driven rapidly back- 
wards and forwards. The furrows of Pinnularia are chambers com- 
municating with the interior of the cell, and in the living state, are filled 
with protoplasm. In the larger forms the protoplasm is often differen- 
tiated into strings. The so-called “ red granules ” of Biitschli (stained 
red by Delafield’s haematoxylin) were detected in a number of diatoms, 
and in some desmids and Ehizopods. They are stained a deep-red 
violet by methj 1-blue. Pyrenoids were observed only in a very few 
instances, forming elliptic or fusiform structures within the chromato- 
phores. A single nucleus is present in all diatoms; in the resting 
condition it has a reticulate honeycomb-like framework. It is always 
nucleolated. In some large species a centrosome is seen near the 
nucleus ; as long as the nucleus is in a resting state, there is never more 
than one. The mode of division of the nucleus is always karyokinetic, 
and the various stages of the process are described in detail. 
Spores of Diatoms. — L’Abbe Comte Castracane § gives a resume of 
the evidence on which he has arrived at the conclusion that the most 
frequent mode of reproduction in diatoms is by a process of sporulation 
or production of germs. That the bodies which he regards as diatom- 
spores are not the spores or germs of parasites, he considers to be proved 
* Hedwigia, xxxii. (1893) pp. 257-9. 
t Heidelberger Habit.-Schr., 36 pp., 1 pi. See Bot. Centralbl., liv. (1893) 
pp. 264-5. 
x Verhandl. Naturhist. Ver. Heidelberg, v. (1893) 26 pp., 1 pi. and 1 fig. 
§ Le Diatomiste, ii. (1893) pp. 29-36, 41-9. 
