j6 EDWARD L. RICE. 



in many genera there is a more or less extensive fusion of the 

 reflexed lamella of the outer gill with the mantle and of the 

 inner gill with the body mass, or, posteriorly, with the corre- 

 sponding lamella of the other ctenidium. 



The frequency and prominence of these two opposed processes 

 in development strengthen the conviction earlier expressed ('98) 

 that the lamellibranch gill is an extremely plastic organ and one 

 very liable to adaptive modification. This being the case, it is 

 not an organ of fundamental phylogenetic importance, and has 

 been given an altogether undue prominence in recent classifica- 

 tions of the Lamellibranchiata. 



Ohio Wesleyan University, 

 Delaware, Ohio. 



LITERATURE. 

 Braun, M. 



'78 Postembryonale Entwicklung von Anodonta. Zool. Anzeiger, Vol. I. 

 Drew, G. A. 



'97 Notes on the Embryology, Anatomy and Habits of Yoldia limatula. Johns 

 Hopkins Univ. Circ, Vol. 17. Reprinted in Ann. and Mag. Nat. Hist., 

 Ser. 7, Vol. 1, '98. Preliminary to Drew ('99)- 

 'go. The Anatomy, Habits and Embryology of Yoldia limatula. Mem. Biol. Lab. 

 Johns Hopkins Univ., Vol. 4. Abstract, with slight additions, in Anat. 

 Anzeiger, Vol. 15, '99. 

 'oi The Life History of Nucula delphinodonta. Quart. Journ. Micro. Sci., 

 Vol. 44. 

 Hatschek, B. 



'80 Entwicklungsgeschichte von Teredo. Arbeiten aus dem Zool. Institut zu 

 Wien, Vol. 3. 

 Korschelt, E. 



'91 Ueber die Entwicklung von Dreissena polymorpha Pallas. Sitzungsber. Ges. 

 Naturf. Freunde, Berlin. 

 Lacaze-Duthiers, H. 



'54 Developpement de la Moule comestible, et, en pariiculier, formation des 

 branchies. Compt. Rend., Vol. 39. Essentially preliminary to Lacaze- 

 Duthiers ('56). 

 '56 Memoire sur le developpement des branchies des mollusques acephales lamel- 

 libranches. Ann. Sc. Nat., Ser. 4, Vol. 5. 

 Lankester, E. R. 



'75 Contributions to the Developmental History of the Mollusca. Phil. Trans. 

 Royal Soc. London, Vol. 165. 

 Ley dig, F. 



'55 Ueber Cyclas cornea Lam. Miiller's Archiv f. Anat., Phys., u. wissenschaftl. 

 Medicin. 

 Loven, S. 



'49 Utvecklingen af Mollusca Acephala. Ofversigt af Kongl. Vetenskaps-Aka- 



