ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
451 
stages, — that of uniciliated swarmspores, the encysting and germination 
of the swarmspores, and the parasitism or vegetative condition, with 
formation of zoosporanges and resting spores. The new species, R. 
Messanense , forms a connecting link between Rhizidium , Rhizophidium, 
and Rhizidiomyces. In a new species of Pliycomyces , P. Pirottianus, found 
on horse-dung, the mode of formation of the zygosperm is described, and 
its very peculiar investment in a weft of rigid hyphae which ultimately 
become bifid at the apex and serve to assist in its dissemination. 
The remarkable polymorphism of Mucor racemosus was demonstrated 
by a series of cultures. 
Potato Scab and its Cause.* * * § — M. E. Eoze succeeded in infecting 
healthy from unhealthy potatoes with this disease, which appeared as 
little brown spots on the surface. Beneath some of these spots were 
whitish excrescences, which, on microscopical examination, were found to 
contain mycele of MucedineaB. Still deeper the cells were softened, and 
contained one or two species of mobile bacteria. The co-operation of 
the bacteria and the Mucedineae seemed to result in the formation of the 
little pustuliform cavities, the principal features of this disease. Careful 
examination of the infected tubers showed that their surface was covered 
with minute pale brown spots, which from mere points enlarge into the 
excrescences previously alluded to. Under the Microscope the small 
brown spots were found to be dead epidermal cells containing a Micro- 
coccus stainable with methyl-blue (? methylen) about 0-6 /x in diameter. 
In this Micrococcus pellucidus the author sees the first cause of the potato 
scab, which by preparing a suitable substratum, i. e. dead epidermal cells, 
and exposure of less resistant tissue beneath, permits the invasion of 
other organisms. 
Oidium albicans as a Pathogenic Agent, t — M. Charrin found 
Oidium albicans in a submaxillary abscess. Experiments on animals 
showed that this organism did not thrive in the liver until the glycogen 
was converted, hence it was only found in the larger hepatic vessels. 
The kidneys were crammed with it, and there coexisted acute nephritis 
with almost complete suppression of urine. Both serum and urine showed 
toxic properties, but these were very slight, so that the pathological 
action of this organism is probably mechanical. 
Protophyta. 
Schizopliyceae. 
Movements of Diatoms. — Dr. K. SchilberskyJ adduces further argu- 
ments in favour of the view of Lauterborn and Hauptfleisch § that the 
creeping movement of diatoms is due to delicate threads of protoplasm, 
which pass through pores in the membrane. These threads must 
probably be capable of changes in form, which cause alternate con- 
tractions and elongations similar to those of Rhizopods and of some 
Eoraminifera. The swimming movement of diatoms is probably due to 
* Comptes Rendus, cxxii. (1896) pp. 1012-4. 
t Semaine Med., 1895, p. 247. See Bot. Centralbl., lxv. (1895) p. 216. 
t Bot. Centralbl., lxv. (1896) pp. 33-6. Cf. this Journal, 1892, p. 245. 
§ Cf. this Journal, ante, p. 100. 
