264 ZOOLOGY. 
nervous ganglia much concentrated and protected by an imperfect cartiine 
ginous capsule ; pharyna armed with two teeth like a parrot's beak, be. 
sides an odontophore. Sexes distinct. Usually development is direct, 
with no metamorphosis ; segmentation of the yolk partial, and a primi- 
tive streak is present as in birds and reptiles, 
Order 1. Tetrabranchiata.— With four gills. (Nautilus, living ; Or. 
thoceras, Goniatites, Ammonites, extinct.) 
G-éer 2, Dibranchiata.—With two gills, (Spirula, Belemnites, ex- 
tinct, Sepia, Architeuthis, Loligo, Ommastrephes, Octopus 
Argonauta.) 
TABULAR VIEW OF THE CLASSES OF MOLLUSCA. 
Cephalopoda, 
Cephalophora. 
Lamellibranchiata. 
ne 
Mo.uvusca. 
Laboratory Work.—The cuttles are not easy to dissect. A horizon- 
tal section through the head will show the relations of the cartilaginous 
capsule to the brain, optic nerves and eyes. The nervous ganglia can 
only be traced after tedious dissection. To study the viscera freshly- 
killed specimens are quite essential, 
LITERATURE. 
Mollusea in general.— Woodward + Manual of the Mollusca (Lon- 
don, 1868). Lankester: Art. Mollusca in Encyclopedia Britannica. 
Gould: Invertebrata of Massachusetts (1870). With the works of 
Cuvier, Huxley, Leuckart, Kiener, Sowerby, Say, Reeve, Tryon, H. 
and A. Adams, D’Orbigny, Hancock, Biuney, Verrill, Dall, etc. 
Lamellibranchtata.—Lacaze-Duthiers : treatises in Annales des Sc, 
Nat. Paris, 1854-61; ¢.e., Anomia (1854), Mytilus (1856); and Archives 
, de Zool. Exp. 1883-87; Aspergillum (1883). With essays by Bojanus, 
Lovén, Peck, Mitsukuri, Brooks, Ryder, etc. 
Anatomy and Development of the Oyster.—Brooks: Development of the 
American Oyster (Studies from Biol. Lab., Johns Hopkins Univ., 1. 
1879); The Oyster, Baltimore, 1892. With essays by Ryder, Osborn, etc. ° 
Cephalophora.—Essays by Brooks, Fol, Rabl, Lacaze-Duthiers 
(Dentalium, 1856-57), Purpura (1859), Haliotis (1859), Vermetus (1860), 
Testacella (1887), Lankester, ete. 
Cephalopoda.— Owen ; Memoir on the Pearly Nautilus, 1882. With 
the essays of Miller, Steenstrup, Kélliker, Grenacher, Verrill, etc. 
