DoNKiN^ on Marine Diatomacece. 
15 
of the sand I found to be impossible. I therefore seized 
hold of the nearest bivalve shell which happened to lie in the 
way^ and with this I carefully scooped up the surface of the 
coloured sand. This I emptied into a wide-mouthed^ stop- 
pered bottle^ capable of holding eight ounces, until half full ; 
the other half of the bottle I filled up with salt water. I 
then shook the whole briskly and allowed the bottle to stand 
for a short period. The sand, being composed entirely of fine 
round grains of quartz and the minute fragments of shells, 
settled at the bottom in a few seconds, leaving the diatoms 
all suspended in the water above, and forming by their abun- 
dance a chestnut- coloured cloud, but not more than 1 part 
in 1000 of the whole sand collected. The coloured water 
was then poured into another bottle and formed the gathering, 
while the sand was thrown away. The diatoms, in their 
turn, were separated from the superfluous water by subsi- 
dence, and brought home in l^oz. bottles. In this manner 
I soon found that any quantity could be collected in a pure 
and unmixed condition, affording an excellent opportunity of 
examining their living forms, and one of which I availed 
myself on every occasion. 
After carefully examining materials collected in this way 
from various parts of the beach, I detected not less than 
about 100 species, all these strictly marine, and, with a few 
exceptions, each species in considerable abundance. But I 
was not a little surprised to find that out of this large num- 
ber it was utterly impossible to refer more than forty-eight 
of these to Professor Smithes ' Synopsis.^ I found, too, that I 
had gathered eighteen of the new forms discovered by Pro- 
fessor Gregory in the estuary of the Clyde, and described in 
his various papers on the Glenshira Sand, and in his more 
recent and very valuable contribution on the Marine Dia- 
tomaceous Forms of the Clyde."^ The remaining species, 
above thirty in number, are entirely new and undescribed, 
many of them of great interest and beauty. As, however, a 
description of the whole of these would extend the present 
communication to an undue length, I shall, on this occasion, 
confine myself to a few, and take an early opportunity to 
describe the remainder, together with my future investiga- 
tions on this shore, in a separate paper. 
In recording all the marine species found on the Northum- 
bjian shore, I shall arrange them under the following heads 
for the sake of reference : I. Species described in Professor 
Smithes 'Synopsis.' 11. Species described by Professor Gregory 
* 'Trans. Koyal Soc. Edinb., vol. xxi, part iv. 
