CONTENTS. 



Page. 



I. New or Critical Species of Chitonomyces and Rickia. By Roland 



Thaxter 1 



II. The Velocity of Polymorphic Changes between Solids. By P. W. 



Bridgman 55 



III. Polymorphism at High Pressures. By P. W. Bridgman ... 89 



IV. Theoretical Investigation of the Radiation Characteristics of an 



Antenna. By G. W. Pierce 189 



V. The 'Refractive Body' and the 'Mitochondria' of Ascaris cams 



Werner. By A. C. Walton 253 



VI. Differential Geometry of Two Dimensional Surfaces in Hyperspace. 



By E. B. Wilson and C. L. E. Moore 267 



VII. A Classification of Quadratic Vectors. By F. L. Hitchcock 369 



VIII. The Mountain Ants of western North America. By W. M. 



Wheeler 455 



IX. The Electrical Resistance of Metals under Pressure. By P. W. 



Bridgman 571 



X. New Laboulbeniales, chiefly Dipterophilous American Species. 



By Roland Thaxter 647 



XI. On the Pigmentation of a Polyclad. By W. J. Crozier . . . 723 



XII. The Joxde-Thomson Effect in Superheated Steam: — 1. Experi- 

 mental Study of Heat-leakage. By H. M. Trueblood . . . 731 



XIII. Records of Meetings 807 



Biographical Notices 826 



Officers and Committees for 1917-18 879 



List of Fellows and Foreign Honorary Members 881 



Statutes and Standing Votes 899 



Rumford Premium 913 



Index "... 915 



