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On the Dp:velopment of the Embryo of Purpura lapillus. 
By William B. Carpenter, M.D., F.R.S., F G.S., Presi- 
dent of the Microscopical Society of London, &c. &c. 
(Read December 29tb, 1854.) 
Notwithstanding the large amount of attention which has 
been given by Microscopists, during the last twenty years, to 
the development of the ova of Gasteropod Mollusks, and the 
completeness with which, in particular cases, its successive 
stages have been observed, much still remains to be learned 
respecting it. And this is more especially the case with re- 
gard to the Pectinihranchiate order, which includes not only a 
very large proportion of the entire class, but also comprehends 
those forms which, by general consent, would be regarded as 
its types. For nearly all the most complete series of observa- 
tions yet made, have had for their subjects either Nudibran- 
chiate or Pulmonated Mollusks; the ova of the former pre- 
senting peculiar facilities for examination, in virtue of their 
extreme transparency, and the rapidity with which they undergo 
some of their most important changes, so that these can be 
watched while in actual progress ;* and those of the latter 
having attracted the attention of that large class of naturalists, 
who, not having the opportunity of sojourning at the coast, 
are glad to avail themselves of the opportunities afforded by 
the universal diffusion of Helices, Lymncei, &c., for the prose- 
cution of this kind of research.*!* 
* On the embryonic development of NudihrancMate and Tectibranclnate 
Gasteropods, see especially the admirable memoir of Yogt, on Actceon 
viridis, in 'Ann. des Sci. Nat.,' 3ieme Ser., torn. vi. (1846) ; also Sars, 
on Tritonia, Doris, Aplysia, and Eolls, in ' Wiegmann's Arcliiv.' 1837, 
1840, 1845 ; Van Beneden, on Aplysia, in ' Ann. des Sci. Nat.,' 2ieme 
S^r., torn. XV. (1841) ; Nordmann, on Tergipes, in ' Ann. des Sci. Nat.,' 
3ieme Ser,, torn. v. (1846) ; Allman, on Actceon, in 'Ann. of Nat. Hist.,' 
vol. xvi. (1845) ; and Reid, on Doris, Polycera, &c., in ' Ann. of Nat. 
Hist.,' vol. xvii. (1846). 
t On the embryonic development of the Pulmonated Gasteropods, nu- 
merous memoirs have been published, of which the following are the most 
important: — Prevost, on Lymnceus, in 'Ann. des Sci. Nat.,' torn. xxx. 
(1833) ; Quatrefages, on Lymnceus and Flanorhis, in ' Ann. des Sci. Nat.,' 
2ieme Ser, tom. ii. (1834) ; Laurent, on Umax and Avion, ibid., torn. iv. 
(1835); Jacquemin, on Planorhis, ibid., tom. v. (1836); and in 'Nova 
Acta Acad.,' tom. xviii. (1838) ; Dumortier, on Lymnceus, in ' Nouv. 
Mem. de I'Acad. Eoy. de Bruxelles,' tom. x. (1837) ; also ' Ann. des Sci. 
Nat.,' 2ieme Ser., tom. viii. (1837) ; Van Beneden and Windischmann, 
on Limax, in ' Bull, de I'Acad. Roy. de Bruxelles,' tom. v., No. 5 ; also 
' Ann. des Sci. Nat.,' 2ieme Ser., tom. ix. (1838), and ' Miiller's Archiv.,' 
1841 : Pouchet, on Lymnceus, in ' Ann, des Sci. Nat.,' 2ieme Ser., tom, x, ; 
Rathke, on Lymnceus, Planorhis, and Helix, in * Froriep's neue Notizen,' 
band xxiv. (1842), and ' Wiegmann's Archiv,,' 1848 ; Fred, Muller, on 
Helix, in ' Wiegmann's Archiv,,' 1848 ; and Gegenbaur, on Helix, Szc, in 
' Siebold and KoUiker's Zeitschrift,' 1852. 
VOL. III. C 
