136 
The President's Address. 
though of course it is not unreasonable to conclude that it is 
primarily derived from the vegetable substances on which 
the animal feeds^ its subsequent elimination in a form in 
which the chemical properties are persistent is somewhat 
singular. 
As it appears from Mr. Dobson's observations that the 
substance occurs in considerable quantities, Mr. Busk sug- 
gests that it might be worth collecting for the purpose of 
using in distillation as a substitute for sugar or malt. 
Amongst the papers classed under the head " Botany and 
Vegetable Physiology/^ the first that claims our notice is 
that by Dr. Gregory^ Professor of Chemistry in the Univer- 
sity of Edinburgh, " On the Post-tertiary Diatomaceous 
Sand of Glenshira.^^ 
This is a continuation of a paper commenced in the pre- 
ceding year, containing a description of upwards of 200 
known species of Diatoms, together with some twenty or 
more previously undescribed. The present one adds many 
more new species to the list, while that of the known forms 
is also extended, making a total of some 300 already observed 
in this gathering, unparalleled for richness of yield, and 
which the author intimates will require another paper to 
complete the description. It appears that about 600 slides have 
been carefully examined, a task, however delightful, that must 
have been intensely laborious ; only those who have worked 
in this particular field can be fully alive to the amount of 
labour required. 
Dr. Gregory is doing good service, not only in making us 
acquainted with new forms, but also in a point of equal 
importance, that of drawing attention to the variations of 
form occurring in the same species, in a similar manner to that 
adopted by our late president. Dr. Carpenter, as regards 
some of the Foraminiferse. In fully working out a subject 
of the kind under consideration, it is not the larger and more 
striking forms (the most elaborate, if I may so term them) 
that occasion the greatest amount of labour, but the more 
minute and abundant ones, the oi -noWoi, where some ten or 
a dozen dissimilar Ibrms, to the careless observer, appear as 
one species, until certain slight but constant peculiarities are 
discovered to predominate in some individuals. 
In investigating the smaller Diatoms, especially those with 
minute markings, great assistance may be derived by using 
a moderate power and noting the peculiar colour assumed by 
the frustules, as was pointed out by Professor W. Smith. 
The colour being due not to any inherent dye, but to the 
well-known property of fine, close lines in producing appa- 
