VOLUME 55. 



1. Robinson, B. L. — I. On tiopical American Compositae, chiefly Eupatorieae. II. A. 



Recension of the Eupatoriums of Peru. pp. 1-88, November, 1919. $1.25. 



2. RiTTER, Wm. E. — A Step Forward in the Methodology of Natural Science (an 



Introduction to: The Functional Relation of one Variable to each of a Number of 

 correlated Variables determined by a Method of Successive Approximation to Group 

 Averages. By George F. McEwen and Ellis L. Michael.) pp. 89-133. December, 

 1919. S1.50. 



3. LoTKA, Alfred J. — Contribution to the General Kinetics of Material Transfor- 



mations, pp. 135-153. March, 1920. $.65. 



4. Phili-ips, H. B. and Moore, C. L. E. — Rotations in Space of Even Dimensions. 



pp. 155-lSS. March, 1920. $.83. 



5. Searle, Arthur. — Orbits resulting from Assumed Laws of Motion, pp. 189-207. 



May. 1920. 65c. 



6. Th.vxter, Roland.^- New Dimorphomyceteae. pp. 209-282. May, 1920. $.85. 



7. Lipka, Joseph. — Some Geometric Investigations on the General Problem of 



Dynamics, pp. 283-322. June, 1920. 90c. 



8. Bap .^CK, H. A.— Specific Heat of Ammonia, pp. 323-409. October, 1920. $1.35. 



9. BouLENGER, G. A. — A Monograph of the American Frogs of the Genus Rana. pp. 



411-480. August, 1920. $1.25. 

 10 r.ccords of Meetings; Officers and Committees; List of Fellows and Foreign Honorary 

 Members; Statutes and Standing Votes, etc. November, 1920. $.75. 



(Continued, on page 2 of cover.) 



