Monthly Microscopical 
Pe ea PROGRESS OF MICROSCOPICAL SCIENCE. 107 
Are the Pus-corpuscles derived from the White Blood Cells ?—There 
is no question in microscopic anatomy which has attracted so much 
attention from physiologists as this during the past two or three years, 
and now it seems, according to the researches of M. Picot recently 
laid before the French Academy,* June 20, 1870, that the idea of 
Conheim that the pus-corpuscles are partly produced by the passage of 
the white blood cells through the blood vessels is altogether a mistake, 
is a misinterpretation of the phenomena in point. M. Picot, whose 
memoir was presented by M. Robin, gave a tolerably long account of 
his observations on the circulation of frogs and mammals, and he 
declares most positively that the white blood cells never pass through 
the vascular walls, and that the pus-cells are formed gradually, external 
to the capillaries. He explains the error of Conheim and others, by 
stating that they confounded several focal planes together, and he 
considers that he has demonstrated this in the following way. He 
counted the number of white blood cells in the arrested blood in the 
capillaries, both before and after the quasi-exuded corpuscles appeared. 
In both instances he says the numbers were the same, and this could 
not have been if the white cells had passed outwards. 
A New Peronospora, Parasitic on Cactus.—In a paper read before 
the French Academy on the 13th of June, MM. Lebert and Cohn, of 
Breslau, describe a new species of Peronospora infecting the Cactus. 
Several fine specimens of Cactus were seen to putrefy and decay while 
the external surface seemed healthy. A section through the cellular 
tissue showed it to. be completely disorganized ; the cell-walls being 
quite broken down and the masses of crystals and starch-granules 
being immediately set free upon a glass slide. At the same time there 
was spread throughout the mass a vast quantity of mycelium. This 
latter was in the form of unicellular threads, very long and thin, un- 
dulating in their course, of unequal calibre throughout, and filled 
throughout with colourless vesicles or droplets. They divided nearly at 
right angles and at irregular distances. It was seen on careful exami- 
nation that the mycelium had not originally traversed the substance 
of the cells, but had spread around and between them, thus form’ng 
an elaborate mesh-work. The author, having given a long account of 
the fungus, called it Peronospora cactorum. 
Ameebee and Monads.—The ‘ Proceedings of the Bristol Naturalists’ 
Society,’ } just issued, contains a paper on these forms, by Dr. Henry 
Fripp. The paper is a long one, and was some time since reported 
in full in ‘Scientific Opinion,’ and we need not therefore abstract it. 
But we commend it to the careful study of our readers. It contains 
some original matter, and a careful survey of the work of English and 
Continental workers. 
Ciliary Movements and their Nature.-—Mr. N. E. Green has been 
for some time engaged in observations on Rotifera and other micro- 
scopic animals, with a view to discover the exact character of the 
action of the cilia. In a paper on the subject, which is published 
by him in the ‘Journal of the Quekett Club’ for July, he describes 
* ‘Comptes Rendus,’ June 20th. + Vol. iv. 
VOL. LV. I 
