f f) N T E N T 8 -^-^V 



VRIES (JAN de). Null-Systems in tlie Plane. 28(ï. 



— Ciibio involutions ot' the tirst class. 291. 



— Linear Null-Systems in the Plane. 302. 



— Null-Systems determined by two linear congruences uf rays. 309. 



WAALS (j. D. VAN DER) presents a paper ot' Prof. J. D. van der Waals Jr.: 

 "On the Theory of the Friction of Liquids". I. 743. IL 1283. 



— presents a paper of Prof. J. D. VAN DER Waals Jr. : "On the Theory of the 

 Brownian Movement. A])pendix". 1057. 



WAALS JR. (J. D. VAN D E r). On the Theory of the Friction of Liquids. 743. 

 II. 1283. 



— On the Theory of the Hrowuian Movement. Appendix. 1057. 

 WEBER (s.). The thermal conductivity of neon. 342. 



WENT (f. A. F. c). On the course of the formation of diastase by Aspergillus niger. 479. 



— presents a paper of Dr. C. Spruit P.Pzn. : "Ou the influence of electrolytes on 

 the motility of Chlamydomonas variabilis Dangeard". 782. 



WERTHEIM SALOMONSON (i. K. A.) V. SaLOMONSON (I. K. A. WeRTHEIM). 



wichmann (a.). On Tin-ore in the Island of Flores. 409. 



— On the Secretion of Phosphates in the stems of Djatikapur [Tectona grandis 

 L ]. 968. 



— On the Volcanoes in the Island of Tidore (Moluccas). 983. 

 wiERSMA (E. D.). The Psychology of Conditions of Confusion. 312. 

 wingmarkings (The value of generic and specific characters, tested by the) of Sphin- 



gides. 991. 

 WINKLER (c.)' presents a paper of Dr. D. J. HULSHOFF Pol: "Our equilibrium- 

 organ'. 626. 



— presents a paper of Dr. D. J. Hulshoff Pol: "Cerebellar-ataxia as disturbance 

 of the equilibrium-sensation". 637. 



— presents a paper of Dr. D. J. Hulshoff Pol : "Experimental cerebellar-atactic 

 phenomena in diseases lying extra-cerebellar". 1095. 



WOLTJER JR. (j.). The longitude of Hyperion's pericentre and the mass of Titan. 881. 



— On the perturbations in the motion of Hyperion proportional to the first power 

 of Titan's eccentricity. 1164. 



WYHE (j. w. VAN). On ^:he Nervus Terminalis from man to Araphioxus. 172. 



— On the Anatomy of the Larva of Amphioxus lanceolatus and the Explanation 

 of its \symmetry. 1013. 



X-RAYS (Investigation by means of) of the crystal structure of white and grey tin. I. 



405. II. The structure of white tin. 494. HI. The structure of grey tin. 501. 

 ZEEHUiSEN (H.) and H. Zwaardemaker. On the Sign of the Electrical Phenomenon 



and the Influence of Lyotrojje series observed in this phenomenon. 417. 

 ZEEMAN (p.) presents a paper of Prof. A. Smits : "On the Electrochemical Behaviour 



of Metals". 158. 



— presents a paper of Prof. A. Smits : "The Phenomenon Electrical Supertension". 

 375. 



