12 DoNKiN_, on Marine Diatomacece. 
tain by future investigation) ; and if so^ which I little doubt, 
it will materially assist^ by the facility ofiPered for the study 
of its living form and economy, in solving the question as to 
whether the group, to which it belongs, ought to be classed 
amongst the Diatomacese, from which it has been excluded 
by Professor Smith in his recent ' Synopsis,^ and by others, as 
of a doubtful character. It will .also assist in determining 
whether those various species of the same family, hitherto 
observed only in a fossil or semi-fossil condition, have in the 
living state their frustules aggregated into filaments, or 
whether these exist as separate and independent organisms. 
That the different genera constituting the filamentous 
Algse will, by future investigation, be ultimately classed 
amongst the diatoms, although perhaps as an aberrant sub- 
family, I am inclined to believe. They possess one essential 
characteristic of the Diatomacese, namely, an external sili- 
ceous envelope, rendering their minute forms indestructible, 
either by the lapse of time or by the action of decomposing 
agents, ordinary or extraordinary, by which all other or- 
ganized structures are resolved into their ultimate elements. 
But future observation must determine their relative posi- 
tion to their congeners by a careful study of their mode of 
development, and of the reproduction of their species. 
On the Marine DiATOMACEiE of Northumberland, with a 
Descriptio7i of Eighteen New Species. By Arthur S. 
DoNKiN, M.D. Morpeth, Northumberland. 
(Read October 21st, 1857.) 
Having in the course of the past summer had occasion to 
visit the shores of this county for relaxation and pleasure, I 
embraced the opportunity thus thrown in my way of examin- 
ing to some extent her marine Diatomaceous products; a 
work for which I was in some measure prepared, by having 
for the last few years devoted a portion of my leisure time 
to this particular field of inquiry, more especially in study- 
ing the fresh- water species. 
I must own, toOj that I was in no small degree prompted 
to the undertaking by knowing that the Northumbrian 
waters, have hitherto been, to the microscopist, unexplored 
regions. For, however carefully certain branches of her 
