E 
: 
11 
sented very different appearances ; in fact, some, like the coscinodisci, 
were circular in a front and nearly rectangular in a side view, with a 
line down the centre ; this line showed the junction of the two valves 
which formed the frustule. The cell contents of the frustules were a 
viscid protoplasm called the endochrome, generally of a yellowish or 
brown colour, and contained globular and granular bodies’; of these the 
last had in some cases been seen to rotate within the cell, so forming a 
species of cell circulation. ; 
The mode of increase was by self-division and by conjugation ; 
in the former, the valves separated, the cell contents aggregated on 
opposite sides of the frustules, the primordial utricle foldedin, became 
contracted, and eventually separated, at the same time a new 
siliceous valve was secreted by each half, and the result was two 
diatoms in the place of one. Thismode of growth was said to be very 
rapid. 
In multiplication by conjugation, two frustules lying near each 
other opened at their sutures and exuded their cell contents, which 
coalesced, while the whole was involved in a gelatinous substance, from 
which sprung frustules of larger size than the parents, to which the 
name sporangial frustule was given. - 
The siliceous valves had, from their markings, always been 
favourites with miscroscopists, and, though some complained of too 
much time being devoted to them, yet the question of the nature of 
their markings had been the means of improving objectives, and had 
also led to the designing of various forms of illuminating apparatus 
more or less simple or complicated. 
A very interesting discussion ensued, in which the PresipEnt, 
Messrs. Horne, Ropertson, Wonror, and Hennau took part, the 
last named gentleman drawing especial attention to the researches of 
Dr. Maddox, which, when published, would throw great light on the 
life history of the diatoms. 
The meeting then became a Conversazione, when living diatoms, 
and a great variety of siliceous valves from different localities, were 
exhibited by Dr. Hatuirax, and Messrs. Hennau, R, Guarsyer, and 
Wonror. ' 
Mr. Hennad also exhibited some exquisite micro-photographs of 
diatoms taken by Dr. Maddox, some of them magnified 3,000 diameters, 
