THE NAUTILUS. 11 



AV. S. Strode M. D.. Bernadotte, 111. Unionidae of Illinois R. and 

 tributaries. 



Geo. W. Taylor, Stewartou, Ottawa. Mollusca of Vancouver 

 Province aud Patellidae. 



John H. Thomson, New Bedford, Mass. Helicidae. 



Bryant Walker, Detroit, INIich. Land and Fr. W. Shells of No. 

 America. 



Rev. John Walton, Lakeside, N. Y. Cypraeidae. 



Henry A. Ward, Rochester, N. Y. General Conchology. 



W. W. Westgate, Houston, Tex. Land and Fr. W. Shells. 



Mrs. A. M. Wheldeu, Canipello, Mass. 



Prof. R. P. Whitfield, New York, N. Y. Fossil Forms of the 

 Mollusca. 



Joseph Willcox, Philadelphia, Pa. Fulgur. 



Mrs. M. Burton Willianison, University Cal. Haliotidae and 

 Fissurellidae. 



S. Hart Wright, Penu Yan, N. Y. Unionidae. 



Lorenzo G. Yates, M. D., Santa Barbara, Cal. La)id Shells of 

 the Americas, South of the U. S. 



All applications for membership should be addressed to the 

 Secretary, Charles W. Johnson, AVagner Institute, Philadelphia, Pa. 

 The Rules of the Association were printed in the last number 

 of the Nautilus. 



NOTES AND EXCHANGES. 



The Origin of Species. — The botanist Ball believes that species 

 are produced by the successive variations of individuals continued 

 through generations, and the subsequent dying out of the interme- 

 diate forms. In a recent address he refers to the Escallnnias in this 

 manner: " There are an immense number of forms of this genus in 

 Chili, which would make first-class species if only the intermediate 

 links would hurry and get out of the way." Anybody who has ex- 

 amined the Hemphill series of the Helix strigosa group cannot fail 

 to notice how admirably the theory applies to that shell. And I 

 believe that groups hardly less extensive can be made of the forms 

 of SpJuerixna striatinum, Unio complanatus, the Michigan Anodontus 



