cated in structure. The circum-pallial nerves and the branchial nerves have ganglion cells throughout their length. The otocystic nerves originate directly from the cerebral ganglia. (See pp. 43-48, and figs. 15, 23, 24, and 25.) Sense Organs.— The eyes are numerous and optically arranged for the formation of images. The sense tentacles are exceedingly numerous and of ordinary structure. The otocysts have canals that open at the surface of the body and the otocystic nerves join the cerebral ganglia direct. The otoliths are composed of granular material that may have been introduced from the outside. (See pp. 48-53, and figs. 10, 20, 22, 24, and 26.) · Embryology. The development is normal and rather rapid. (See pp. 53-60, and figs. 27-36.) LITERATURE. I. 2. ANDREWS. Some Activities of Polar Bodies. Johns Hopkins Univ. ANDREWS. Activities of the Polar Bodies of Cerebratulus. Arch. 3. BROOKS. The Origin of the Oldest Fossils and the Discovery of the Bottom of the Ocean. Smithsonian Report for 1894 (also Salpa. 4. BROOKS. The Development of the American Oyster (Ostrea virginiana). Stud. Biol. Lab. Johns Hopkins Univ., Vol. 1, 1880. 5. DREW. Yoldia limatula. Memoirs from the Biol. Lab. of the Johns Hopkins Univ. Vol. 4, No. 3, 1889. 6. DREW. Locomotion in Solenomya and its Relatives. Anat. Anz. Bd. XVII., No. 15, 1900. 7. DREW. The Life-History of Nucula delphinodonta. Quart. Jour. of Micro. Sci. Vol. 44, Part 3, New Series, 1901. 8. GRAVE. Investigations for the Promotion of the Oyster Industry of North Carolina. U. S. Fish Com. Report for 1903. 9. HATSCHEK. Ueber Entwickelungsgeschichte von Teredo. Arb. Zool. Inst. Wien. Bd. 3, 1880. IO. II. HEATH. The Development of Ischnochiton. Zool. Jahrb., Abth. f. HYDE. The Histology of the Eye of Pecten. Mark Anniversary 12. JACKSON. Phylogony of the Pelecypoda. Memoirs Boston Soc. Nat. Hist. Vol. IV., No. 8, 1890. 13. JAMESON. On the Origin of Pearls. Proc. Zool. Soc. London, 1902. 14. KELLOGG. A Contribution to our Knowledge of the Morphology of Lamellibranchiate Mollusks. Bul. U. S. Fish Com. Vol. X., 1890. 15. KELLOGG. The Ciliary Mechanism in the Branchial Chamber of the Pelecypoda. Science (2), Vol. II. 16. KOWALEVSKY. Embryogénie du Chiton Polii (Philippi) avec quelques Remarques sur le Développement des Autres Chitons. Ann. Mus. Hist. Nat. Marseille. T. 1, No. 5, 1883. 17. LACAZE-DUTHIERS. Historie de l'Organisation et du Développement du Dentale. Ann. des Sci. Nat. Ser. 4, VII., 1857. 18. 19. 20. 21. 22. 23. 24. MEAD AND BARNES. Observations on the Soft-clam. (Fifth paper). Rhode Island, 34th Ann. Report of the Com. of Inland Fisheries, 1904. MEISENHEIMER. Entwicklungsgeschichte von Dreissensia polymor- PATTEN. Eyes of Molluscs and Arthropods. Mitth. Zool. Stat. PATTEN. The Embryology of Patella. Arb. Zool. Inst. Univ. Wien. PELSENEER. Contribution á l'Etude des Lamellibranchs. Arch. de PRUVOT. Sur le Développement d'un Solénogastre. Compt. rend. RISSER. Habits and Life-History of the Scallop (Pecten irradians). Rhode Island, 31st Ann. Report of the Com. of Inland Fisheries, 1901. 25. RICE. Die Systematische Verwertbarkeit der Kiemen bei den Lamellibranchiaten. Jen. Zeit. f. Naturwiss. Bd. XXXI., 1897. 26. SCHREINER. Die Augen bei Pecten und Lima. Bergens Mus. Aarbog, 1896. 27. SIGERFOOS. The Pholida. Notes on the Early Stages of Development. Johns Hopkins Univ. Circ. Vol. 14, 1895. 28. SMITH. The Giant Scallop Fishery of Maine. Bul. U. S. Fish. Com., Vol. IX., 1889. 29. STEMPELL. Beiträge zur Kenntniss der Nuculiden. Zool. Jahrb. Sup. 4. Fauna Chilensis, Heft 2, 1898. 30. STEMPELL. Zur Anatomie von Solemya togata. Zool. Jahrb. Bd. 31. STENTA. Zur Kenntniss der Strömungen im Mantelraume der Lamellibranchiaten. Arb. Zool. Inst. Univ. Wien. Bd. XIV., 1902. 32. ZEIGLER. Die Entwickelung von Cyclas cornea. Zeit. f. Wiss. Zool. Bd. 41, 1885. ba'. ba". bg. bn. bs. Blood space. bv. Branches of the branchial artery. Branches of the branchial artery in the modified filaments. Byssal gland. Branchial nerve. Branchial vein. cpm'. Circular pallial muscles of the infolded ridge. fs. Filament support, probably to keep the filament from swelling into a cylindrical shape with the pressure of the blood. pa. pa'. paa. pas. pas'. Posterior adductor muscle, anterior portion. Posterior adductor artery. Posterior adductor muscle scar, anterior portion. Posterior adductor muscle vein. Pedal ganglion. Pallial line. pav. Pg. pl. pn. Palp nerve. |