T. Bland on the Geographical Distribution of Mollusca. 389 
it as a new individual, or at all events a distinct member of a 
series of forms constituting collectively the representatives of the 
_ Equisetacee.—The first discovery of the analogy between the 
developments from the spore in germination, in the Ferns and 
Eqguisetacee, is due to M. G. Thuret,t who saw the spores of the 
latter produce a cellular pro-embryo somewhat like that of the 
ferns, and in this were developed antheridia of analogous struc- 
ture, emitting cellules containing many spiral filaments. 
This announcement was confirmed by M. Milde,{ whose ob- 
servations extended over some months, during which time no 
‘ovule’ was produced, but he saw what appeared to be the rudi- 
ment of one. Dr. Mettenius states that he has met with decay- 
ing ‘ovules’ precisely like those of the ferns, upon the pro-embryo 
of an equisetum, and thus the evidence is completed, so far as 
the occurrence of the two kinds of organs is concerne 
, (To be continued.) 
eee 
Arr. XXXVIL—Facts and Principles Relating to the Origin 
and the Geographical Distribution of Mollusca ; by Tomas 
_ Buanp, F.G.S., London. 
_ Iv preparing this paper, the following works have been par- 
ticularly consulted, viz,—Jntroduction to the Mollusca of the 
United States Exploring Expedition. By A. A. Gout, 
December, 1851; and Catalogue of Shells collected at Panama, 
and Geographical Lis- 
tribution. By C. B. Avams, Professor of Zoology, &c. in Am- 
s as highly valuable contributions to 
Science, and especially so with respect to the subject of the 
geographical distribution of Testaceous Mollusca. 
The attention of these authors has for some years 
to this question. It is discussed by D 
on the Invertebrata of Massachusetts, 
i, Nat., , vol. xi, 5. 
Sioa P B06. Se oe potalk, 1860, p32. 
____Secoxp Serres, Vol. XIV, No. 42.—Nov., 1852. 50 
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