34 
PROGRESS OF MICROSCOPICAL SCIENCE. 
named tlie genus after the same genus of Professor Sars, hut the species 
after Mr. Carter, F.R.S. 
Miasm viewed with the Microscope . — A series of researches, rather 
like those conducted some six years ago by Professor Salisbury, M.D., 
of Ohio, U. S. A., have been conducted by M. Bolestra, and recorded 
in the * Comptes Rendus ’ of the French Academy. The water of 
the Pontine Marshes, and of similar malarious regions, he found 
to contain invariably, along with the common infusoria, a minute 
algoid vegetation, with an abundance of transparent, greenish-yellow 
spores, yqVf mm - diameter. This vegetation develops slowly in 
pure water and at low temperatures, hut rapidly in the heat of the sun 
and amid decomposing organic material. It floats upon the water, 
giving an iridescent film when young, and its spores are found in the 
air near the marshes, and even at Rome, being most abundant in warm 
weather, and after a rain or during a fog, and least so in a cool, dry 
atmosphere. M. Bolestra regards these spores as the miasmatic agent 
in the production of the intermittent fevers for which the localities are 
badly celebrated. 
A Conspectus of the Diatomacece . — Professor W. H. Smith has sent 
us the 2nd part of his ‘ Memoir on the Diatomaceae,’ which he pur- 
poses to go on with till it is completed. We observe with some 
satisfaction that the author has been at some pains to explain the more 
recent views of diatomacean structure in this part, which he did not do 
in the preceding one .Still, however, it is evident from the date of pub- 
lication, that this was done before our previous remarks had come under 
his notice. He believes that all the frustules are “ siliceous boxes,” 
with either one portion (the cover) slipping over the other, as in Pin- 
nularia, or with edges simply opposed, as in Fragilaria. If we take a 
frustule of Melosira, it may be compared to a pill-box — one portion 
slipping on to the other. The great majority of diatoms are thus 
constituted. It is perfectly evident that, in the case of the formation 
of a new valve, in the processes of self-division, this new part, which 
slips out from the older, must be somewhat smaller. Inside of the 
box is a membrane, inclosing the internal coloured or colourless sub- 
stance, imbedded in which may always be seen, at least in the larger 
forms, a distinct nucleus, sometimes two, and sometimes a “ germinal 
dot,” with numerous fine threads radiating from the nucleus, or the 
germinal dot. As the frustule increases in width, one portion slips 
out from the other, and sometimes successive additions of siliceous 
matter are made to the edges of the box, somewhat analogous to the 
successive additions to the edge of the shell of a mollusc. When the 
widening of the frustule has reached a certain extent, the lining mem- 
brane at the places which would be exposed if the two portions were 
wholly to slip apart, infolds. He has reason to believe that, previous 
to this, a double membrane of extreme tenuity has been formed, com- 
mencing its growth at the nucleus (which itself is divided), and ex- 
tended to the margins of the cell, which is thus divided into two 
nearly equal parts ; for as soon as this infolding commences (perhaps 
now accelerated by the admission of water), the line of division can 
