CONTENTS. XXI 
VRIES (HUGO DE) presents a paper of Prof. J. M. Janse: “An investigation on 
polarity and organ-formation with Caulerpa prolifera”. 420. 
VRIES (JAN DE). The congruence of the conics situated on the cubic surfaces of 
a pencil. 264. 
— A congruence of order two and class two formed by conics. 311. 
— On a special tetraedal complex. 572. 
— On a group of complexes with rational cones of the complex. 577. 
— A group of algebraic complexes of rays. 627. 
— On nets of algebraic plane curves. 631, 
— On linear systems of algebraic plane curves. 711. 
— Some characteristic numbers of an algebraic surface. 716. 
WAALS (VAN DER) y-surface (Contributions to the knowledge of). IX, The conditions 
of coexistence of binary mixtures of normal substances according to the law of 
corresponding states. 222, 
WAALS (J. D. VAN DER) presents a paper of B. M. van DAurseN: “On the 
function - for multiple mixtures”. 94, 
D 
— The derivation of the formula which gives the relation between the concentra- 
tion of coexisting phases for binary mixtures. 156. 
— presents a paper of G. C, Grerrars: “On Px-curves of mixtures of acetone and 
ethylether and of carbontetrachloride and acetone at O°C’. 162. 
— presents a paper of Dr. Ca. M. van Deventer: “On ihe melting of floating 
ice”. 459. 
— The transformation of a branch plait into a main plait and vice versa. 621. 
— presents a paper of Dr. Pu. Kounstamm: “A formula for the osmotic pressure 
in concentrated solutions whose vapour follows the gas laws.” 723. 
-— presents a paper of Dr. Pa, KounstamM: “Kinetic derivation of van ’r Horr’s 
law for the osmotic pressure in a dilute solution”. 729. 
— presents a paper of Dr. Pu, KounstamMm: ‘Osmotic pressure and thermodynamic 
potential”. 741. 
WATER (On the origin of the fresh-) in the subsoil of a few shallow polders. 53. 
— (The viscosity of the system hydrazine and), 329. 
— of our sea-provinces (Some considerations en the conclusions arrived at in the 
communication made by Prof, Eve. Dugors, entitled: Some facts leading to trace 
out the motion and the origin of the underground). 45. 
WEEDER (J.). A new method of interpolation with compensation applied to the 
reduction of the corrections and the rates of the standardclock of the Observa- 
tory at Leyden, Hohwii 17, determined by the observations with the transitcircle 
in 1903, 241. . 
— Approximate formulae of a high degree of accuracy for the relations of the 
triangles in the determination of an elliptic orbit from three observations, 752. 
WENT (F.A. F.C.) presents a paper of H. P Kuyper: “On the development of 
the perithecium of Monascus purpureus Went and Monascus Barkeri Dang.” 83. 
