CONTENTS. 



Page 



I. Studies on Fluorite : (IV.) The Kathodo-Luminescence of Fluorite. 



By H. W. Morse 1 



II. (I.) New Species of Senecio and Schoenocaulon from Mexico. By 

 J. M. Greenman. (II-) New or otherwise Noteivorthy Sper- 

 matophytes, chiefly from Mexico. By B. L. Robinson. (HI.) 

 New Plants from Guatemala and Mexico collected chiefly by 

 C. C. Deam. By B. L. Robinson and H. H. Bartlett. 

 (IV.) Diagnoses of Neio Spermatophytes from Mexico. By 

 M. L. Fernald 17 



III. Maturation Stages in the Spermatogenesis of Vespa maculuta Linn. 



By E. L. Mark and Manton Copeland 69 



rV^. The Physiological Basis of Illumination. By Louis Bell . . 75 



V. On the Determination of the Magnetic Behavior of the Finely Divided 

 Core of an Electromagnet lohile a Steady Current is being 

 Established in the Exciting Coil. By B. O. Peirce ... 97 



VI. The Demagnetizing Factors for Cylindrical Iron Rods. By C. L. B. 



Shuddemagen 183 



VII. Outlines of a New System of Thermodynamic Chemistry. By 



G. N. Lewis 257 



VIII. The Quantitive Determination of Arsenic by the Gutzeit Method. 



By C. R. Sanger and O. F. Black 295 



IX. The Determination of Arsenic in Urine. By C. R. Sanger and 



O. F. Black 325 



