34 BIOLOGICAL SOCIETY OF WASHINGTON. 



Prof. C. V. Riley read a paper entitled On the Philosophy of 

 THE Retardation of Growth among Lower Animals.* A dis- 

 cussion followed, participated in by Messrs. Ulke, White, Gill, Earll, 

 King, and Ward. Dr. C. A. White read a paper entitled An- 

 tiquity OF Certain Types of North American Non-Marine 

 MoLLUSCA, AND THE EXTINCTION OF OTHERS. f This paper was dis- 

 cussed by Messrs. Gill and Dall. 



Eighteenth Meeting, November 25, 1881. 



The President occupied the chair. Thirty-four members were 

 present. 



Mr. Richard Rathbun presented a communication On the Re- 

 cent Explorations of the U. S. Fish Commission. After 

 sketching the history of the Commission since its organization, in 

 1871, and describing the new exploring steamer ''Fish Hawk," 

 he spoke at some length of the wonderful wealth of life discovered 

 in 1880 and i88r on the inner edge of the Gulf Stream, about one 

 hundred miles off Newport and Martha's Vineyard. Mr. Rathbun's 

 remarks were illustrated by numerous specimens, and a large model 

 of the steamer ''Fish Hawk." Messrs. Gill, Dall, Goode, and 

 Schaeffer took part in the discussion of this paper. 



Nineteenth Meeting, December 9, 1S81. 



The President occupied the chair. Forty members were present. 



Col. Marshall McDonald described some recent observations upon 

 young shad in confinement. Prof. L. F. Ward read a paper on 

 The Causes of the Absence of Trees on the Great Plains. J 



*i882. Riley, Charles V. Retarded Development in Insects. <^Pi-o- 

 ceedings, Amer. Assoc. Adv. Sci., XXX, Cincinnati Meeting, and in separate 

 "Retarded Development, &c.," pp. 4. (February, 1882.) 



•j-1882. White, Charles. A. On Certain Conditions attending the Geological 

 Descent of some North American types of Fresh-water Gill-bearing MoUusks. 

 <American Journal of Science and Arts. XXIII. 1S82, (May.) pp. 382-6. 

 Annual Report of the U. S. Geological Survey for 1882. 



J 1882. Ward, Lester F. On the Cause of the Ab.sence of Trees on the 

 Great Plains. <^ Kansas City Review of Science and Industry. V. 1882, 

 pp. 697-702, (March.) 



