36 
On the Siliceous Organisms /om?zc? in the Digestive Cavities 
of the Salp^^"^ and their relation to the Flint Nodules 
of the Chalk Formation. By Surgeon G. C. Wallich^ 
M.D., Retired List H.M. Indian Army. 
(Read December 14tli, 1859.) 
However difficult may be tlie task of investigating suc- 
cessfully the phenomena peculiar to the minute animal and 
vegetable forms by which we are immediately surrounded on 
land^ it is trifling in comparison with the task of conducting 
similar investigations at sea. The haunts of the organisms 
frequenting our streams, lakes, rivers, and even the shallower 
seas, are all fixed by something like definite boundaries, within 
which we may generally assure ourselves of their presence, 
or, if needs be, devise means for their capture. Not so, how- 
ever, with the minute inhabitants of the open sea ; for, there, 
we are at once met by a series of most perplexing obstacles 
to research ; and, did no indirect means present themselves 
whereby it might be carried on, the prospect would, in all 
probability, be hopeless. But, fortunately, we possess, in 
some of the lower forms of animal life, a class of microphagic 
collectors, who, living in the element surcharged with the 
material we seek for, gather it together for their sustenance, 
and are, at the same time, easily captured. The Salpse stand 
foremost amongst those creatures, being almost universally dis- 
tributed through the open sea, and frequently occurring in such 
vast multitudes, as to cover the surface for many square miles, 
and impart to the water the consistence of a jelly. Indepen- 
dently, therefore, of the interest which has attached to the 
Salpse, since Chamisso discovered, in their reproductive pro- 
cess, the remarkable phenomena to which he applied the 
term Alternation of generations,^^ they exhibit a faculty of 
the highest value to the microscopist ; and there cannot be a 
doubt that, under a systematic examination of the Salpean 
alimentary matter, obtained from various latitudes, we should 
speedily be enabled to accumulate a mass of facts, not only 
of importance to microscopical science, but to the natural 
history of the sea generally. 
I am somewhat desirous of laying stress on this source of 
* Although the Salpee are especially referred to in this comrfiunication, 
ill order to avoid repetition, it is intended to embrace under this head, the 
whole of the molluscoid tribes that frequent the open sea in shoals, and live 
upon the microscopic organisms it contains. 
