264 ZOOLOGY. 



nervous ganglia much concentrated and protected by an imperjrct ctirtila- 

 ginous capsule ; pharynx 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.) 



Order 2. Dibranchiata. With two gills. (Spirula, Belemnites, ex- 

 tinct, Sepia, Architeuthis, Loligo, Otnrnast re plies, Octopua 

 Argonauta.) 



TABULAR VIEW OF THE CLASSES OF MOLLUSCA. 

 Cephalopoda, 



Cephalophora. 



Lam ellib ranch iata. 



MOLLUSCA. 



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. 



Mollusca in general. Woodward : Manual of the Mollusca (Lon- 

 don, 1868). Lankester: Art. Mollusca in Encyclopaedia Britanuica. 

 Gould: Invertebrata of Massachusetts (1870). With the works of 

 Cuvier, Huxley, Leuckart, Kiener, Sowerby, Say, Reeve, Tryon, H. 

 and A. Adams, D'Orbiguy, Hancock, Biuney, Verrill, Dall, etc. 



Lamellibranchiata. Lacaze-Duthiers : treatises in Anuales des Sc. 

 Nat. Paris, 1854-61; i.e., Auomia (1854), Mytilus (1856); and Archives 

 de Zool. Exp. 1883-87; Aspergillum (1883). With essays by Bojauus, 

 Loveu, Peck, Mitsukuri, Brooks, Ryder, etc. 



Anatomy and Development of tlie Oyster. Brooks: Development of the 

 American Oyster (Studies from Biol. Lab., Johns Hopkins Univ., i. 

 1879); The Oyster, Baltimore, 1892. With essays by Ryder, Osborn, etc. 



Cephalophora. Essays by Brooks, Fol, Rabl, Lacaze-Duthiers 

 (Deutalium, 1856-57), Purpura (1859), Haliotis (1859), Vennetus (I860), 

 Testacella (1887), Lankester, etc. 



Cephalopoda. Owen : Memoir on the Pearly Nautilus, 1832. With 

 the essays of Mitller, Steenstrup, Kolliker, Grenacher, Verrill, etc. 



