CONTENTS XXI 
Mathematics. ARN. DenNsoy: “Sur une propriété de séries trigonométri- 
ques”’. 220. 
— L. E. J. Brouwer: “Ueber eineindeutige, stetige Transformationen 
von Flachen in sich.” (siebente Mitteilung). 232. 
~ JAN DE Vries: “An involutory transformation of the rays of space 
which is defined by two involutory homologies.” 462. 
— JAN DE Vries: “An involution of rays defined by a congruence of 
REYE and an involutory homology.” 466. 
— J. Worrr: “On the theorem of Picarp.’ 585. 
— W. VAN DER WoubeE: “On the motion of a fixed system.” 589. 
— K. W. Rotacers: “Degenerations in linear systems of plane cubics.” 797. 
— F. BERNSTEIN: “Die Integralgleichung der elliptischen Thetanullfunktion. 
2e Note: Allgemeine Lösung.” 817. 
— B. P. HAALMEYER: “On elementary surfaces of the third order.” (fifth 
comm.). 920. 
— L. E. J. Brouwer: “Intuitionistische Mengenlehre.” 949. 
— L. E. J. Brouwer: “Besitzt jede reelle Zahl eine Dezimalbruch- 
entwickelung ?” 955. 
— H. J. vaN VEEN: “Properties of congruences of rays.” 1206. 
— J. W. N. re Heux: “Explanation of some interference curves of 
uniaxial and biaxial crystals by superposition of elliptic pencils.’ 1223. 
— J. GC. Kruyver: “On analytic functions defined by certain LAMBERT 
series.” 1226. 
— JAN DE Vries: “Two representations of the field of circles on point- 
space.” 1323. 
— N. G. W. H. Beecer: “Bestimmung der Klassenzahl aller Unterkörper 
des Kreiskörpers der m- ten Einheitswurzeln.” (Verbesserung). 1399. 
MATHIAS (E.), C. A. CROMMELIN and H. KAMERLINGH ONNES. The recti- 
linear diameter of hydrogen. 1175. 
MENGENLEHRE (Intuitionistische). 949. 
Mercury (On the critical quantities of) in connection with the increase of 
the molecular attraction on dissociation of the double molecules. I. 
267. 115 282. 
MerostomaTa (Die Verwandtschaft der) mit den Arachnida und den 
anderen Abteilungen der Arthropoda. 739. 
MESOZOIC DEEPSEA DEPOSITS (On manganese nodules in) of Dutch 
Timor. 997. 
Merars (A thermo-electrical differential method for the determination of 
transition points of) at comparatively low temperatures. 977. 
— (On the acceleration of solubility of) in acids by reducible 
compounds. 1449. 
