GEAY AND TURTON’S MANUAL OF BRITISH SHELLS. 
157 
likely to be found. As yet they are but unseen potentialities, of which 
the eye has hitherto been unable to detect any concrete or objective 
manifestation.” 
We have several instances given of spontaneous fission existing 
amongst the soft animals of the Foraminifera. “ In each of these exam¬ 
ples,” says ProfessorWilliamson, “there appears to have been an abortive 
attempt at division of the uncalcified germ, which attempt the prema¬ 
ture supervention of the calcifying process has arrested. Whenever such 
specimens occur, it invariably happens that the two halves of the twin 
organism belong to the same variety or type, and these specimens indicate 
that fission tends to repetition of identical types, and not to differentia¬ 
tion.” 
We have some very useful information given as to the localities and 
modes of collecting these creatures. Fifty-six species, or so-called 
species, are described, with an endless number of varieties. We cordially 
agree with the author, that the time has not yet arrived when we can 
pronounce which is a species, and which a variety. The Plates, seven 
in number, are most beautifully executed by Tuffen West, and we trust 
will help to illustrate the promised “Introduction,” which may we live 
to see! 
Manual of Land and Fresh-water Shells of the British Islands ; 
with Figures of each of the Species by W. Turton, M. D. Hew Edi¬ 
tion, with Additions by J. Edward Gray, Ph.D., F. E. S., &c. 8vo, 
with twelve Plates and numerous Woodcuts. London; Longman 
and Co. 1857. 
It is now something more than a quarter of a century since Dr. W. Turton 
published his “Manual of the Land and Fresh-water Shells of the British 
Islands,” and we wonder what he would have said or thought if he had 
lived to see the pretty volume whose title stands at the head of this 
notice grow out of his own thin octavo of some 150 pages. We have 
some doubts ourselves whether the little volume of 1831 is not as useful 
as its great fat grandchild of 1857. We think that there is a want 
of some manual of both the marine, and land and fresh-water Mollusca 
(if for convenience we allow this arbitrary division), which, without 
incumbering the student with anatomical details or well worked-out 
synonymic lists, shall afford him fair diagnoses of the families and genera, 
and such descriptions of the species as may enable him to be pretty cer¬ 
tain of the native ones, referring him all the time to the classic volumes 
of Forbes and Hanley for matters of detail. This desiderata, even as 
regards the land and fresh-water shells, is not, in our opinion, supplied 
by this volume of Dr. Gray’s, for the original 150 pages of Turton have 
well nigh completely vanished from the book. It aspires more to the 
vol. v.— rev. 2 a 
