74 



ESSAY ON CLASSIFICATION. 



Part I. 



in their development than tlie Lamellibranchiata. Even among the terrestrial and 

 aquatic Pulmonata there are striking diiferences. Some of the Pectinibranchiata are 

 remarkable for the curious cases in which their eggs are hatched and the young 

 developed, to an advanced state of growth. The cases of Pyrula and Strombus are 

 among the most extraordinary of these organic nests. The embryology of Cepha- 

 lopods^ has been masterly illustrated by KtiUiker. 



There is still much diversity of opinion among naturalists, respecting the limits 

 of Articulata; some being inclined to separate the Arthropoda and Worms as tlis- 



f. wiss. Zool., 18.j0, vol. 2, p. 12.5. — Kolliker, 

 (A.,) q. a., Zeitsch. f. wiss. Zool., vol. 4, p. 333 and 

 369. — MiJLLER, (.J..) Ueber verscliiedene Formeii 

 von Seethieren, Muller's Arch., 1854, p. 69. — Ueber 

 Synapta digitata und iiber die Erzeugung von 

 Schnecken in Holothurien, Berlin, 1852, 4to. fig. — 

 The remarkable case described in this paper, admits 

 of an explanation which Miiller has not considered. 

 It is known, that fishes penetrate into the cavity of 

 the body of Holothuria;, through its posterior open- 

 ing. (De Bosset, Notice, etc., Mem. Soc. Sc. Nat., 

 Neuch., 1839, voh 2, 4to.) The similarity of Ento- 

 concha mirabilis with the embryonic shell of various 

 species of Littorina?, such as Lacuna vincta, the 

 development of which I had an opportunity of study- 

 ing, suggests the possibility, that some species of this 

 family, of which there are many very small ones, 

 select the Synapta as their breeding place and leave 

 it after depositing their eggs, which may become con- 

 nected with the Synapta, as our Mistletoe or the 

 Orobanche and many other parasitic plants, with the 

 plants upon which they grow. — Gegenbauer, (C.,) 

 Beitrage zur Entwickelungsgeschichte der Landgas- 

 teropoden, Zeitsch. f wiss. Zool., 1852, vol. 3, p. 371. — 

 Untersuchungen iiber Pteropoden und Heteropoden, 

 Leipzig, 1855, 1 vol., 4to. fig. — Kouen, (.J.,) und 

 Danielssen, (D. C) Bitrag til Pectinibranchiernes 

 Udviklingshistorie, Bergen, 1851, 8vo. ; French Ann. 

 Sc. Nat., 1852, vol. 18, p. 257, and 1853, vol. 19, 

 p. 89; also Germ, in Wiegm. Arch., 1853, p. 173. — 

 NoRDMANN, (Al. V.,) Versuch einer Monographie 

 von Tergipes Edwardsii, St. Petersburg, 1844, 4to. — 

 Lecckart, (R.,) Zoologische Untersuchungen, Gies- 

 sen, 1853-54, 4to., fig., 3d Fasc — Huxley, (Th. H.,) 

 On the Morphology of the Cephalous Mollusca, etc.. 



Phils. Trans. R. Soc, 1853, L, p. 29. — Hogg, 

 (Jabez.) On the Development and Growth of the 

 Watersuail, Quart. Micr. Journ., 1854, p. 91. — Reid, 

 (J.,) On the Development of the Ova of the Nudi- 

 branchiate Mollusca, Ann. and Mag. Nat. Hist., 1846, 

 vol. 17, p. 377. — Carpenter, (W. B.,) On the 

 Development of the Embryo of Purpura Lapillus, 

 Quart. Micr. Journ., 1845, p. 17. 



^ Kolliker, (Alb.,) Entwickelungsgeschichte 

 der Cephalopoden, Zurich, 1844, 4to., fig. — Van- 

 Beneden, (P. J.,) Recherches sur rEmbryogenie 

 des Sepioles, N. Mem. Acad. Brux., vol. 14, 1841. 

 — Coldstream, (Z.,) On the Ova of Sepia, Loud, 

 and Ed., Phil. Mag., Oct., 1833. — Duges, (Ant.,) 

 Sur le developpement de I'embryon chez les Mollus- 

 ques Cephalopodes, Ann. Sc. Nat., vol. 8, p. 107. — 

 RathivE, (H.,) Perothis, ein neues genus der Cepha- 

 lopoden, Mem. Ac. St. Petersb., 1834, vol. 2, p. 

 149. (Is the young of some Loligoid Cephalopod.) 

 Milne-Edwards, (H.,) Observations sur les spei'- 

 matophores des Mollusques Cephalopodes, etc., Ann. 

 Sc, n., 2de ser., vol. 3, p. 193. — Kollikek, (A.,) 

 Hectocotylus Argonauts Delle Chiaje und Heet. 

 Tremoctopodis K., die Miinnchen von Argonauta 

 Argo und Tremoctopus violaceus, Ber. Zool. Anst. 

 Wurzburg, 1849, p. 69. — Muller, (11..) Ueber 

 das Mfinnchen von Argonauta Argo und die Hecto- 

 cotylen, Zeitsch. f. wiss. Zool., vol. 4, p. 1. — Vera- 

 NY, (J. B.,) et Vogt, (C.,) Memoire sur les Hec- 

 tocotyles et les males de quelques Cephalopodes, 

 Ann. Sc. n., 3e ser., 1852, vol. 17, p. 147. — Rod- 

 LiN, (F. D.,) De la connaissance qu'ont cue les 

 anciens du bras copulateur chez certains Cephalo- 

 podes, Ann. Sc. n., 3e son, 1852, vol. 17, p. 188. — 

 Leuckart, (R.,) Zool. Unters. q. a. 



