92 
The Presidenfs Address, 
Greville, of Edinburg]i_, has communicated a paper describing 
several new forms of the beautiful Diatomaceous genus Campy - 
lodiscus. Mr. Roper_, in a paper on Triceratium arcticum, 
has shown that this genus must no longer be regarded as a 
non- catenated form of Diatomacess^ as in its natural state its 
triangular frustules are connected together as in many other 
forms of this family. The last contribution on Diatomacese 
is by Dr. Wallich^ who, in his paper " On the Siliceous Orga- 
nisms found in the Digestive Cavity of Salpse, and their rela- 
tion to the Flint Nodules of the Chalk Formation/^ has 
endeavoured to account for the presence of forms of Diato- 
macese and Desmidese in the flints and siliceous nodules of 
the chalk_, by their having been collected by Salpse in their 
stomachs, then swallowed by whales or other large animals, 
and, on the death of these creatures, been deposited in the 
bed of the ocean, in the concretionary form in which they 
are now found. 
We may learn from these papers how great an interest 
attaches to the study of the Diatomacese, and how some of 
the highest problems in the history of the life upon our globe 
may be solved by their study. Formed of imperishable 
material, and, once formed, not experiencing the decay which 
is the law of every other existing organism, these minute 
beings leave behind them the most extensive record of their 
existence. Not only can we examine their forms, many of 
which are exquisite from their graceful outline and delicate 
carving, but even with regard to extinct species, we may 
gather the history of their habits and mode of increase, and 
other points, from the localities in which they are found. 
Independent, however, of the interest which attaches to the 
study of the Diatomacese as a group of organized beings pre- 
senting us, as it were, with the first struggles of life against 
the physical and chemical forces of brute matter, they are 
capital objects with which to train the eye and mind to habits 
of correct observation. It is in this group of beings that the 
advanced microscopist seeks for the severest tests with whicli 
to try the highest powers of his object-glasses ; and it is in 
the observation of the forms and markings of these the most 
delicate productions of the Creative Hand that the young 
microscopist will best acquire the habit of distinguishing- 
minute diflPerences and resemblances. 
An interesting communication was read at our June 
meeting, from Mr. George F. Pollock, containing "Obser- 
vations on Granulated Blood Discs. ^' This paper indicates 
that, however well the blood- discs may have been observed, 
