KONINKLIJKE AKADEMIE VAN WETENSCHAPPEN 
TE AMSTERDAM. 
PROCEEDING Ss 
VOLUME XIX 
N°. 9 and 10. 
President: Prof. H. A. LORENTZ. 
Secretary: Prof. P. ZEEMAN. 
(Translated from: “Verslag van de gewone vergaderingen der Wis- en 
Natuurkundige Afdeeling,’ Vol. XXV). 
CONTENTS. 
JAN DE VRIES: “Two null systems determined by a net of cubics”, p. 1124. 
K. W. WALSTRA: “On a Representation of the Plane Field of Circles on Point-Space”. (Communi- 
cated by Prof. JAN DE VRIES), p. 1130. 
CHS. H. VAN OS: “A Quadruply Infinite System of Point Groups in Space”. (Communicated by Prof. 
JAN DE VRIES), p. 1133. 
J. F. VAN BEMMELEN: “The colourpattern on Diptera wings”, p. 1141. 
A. SCHIERBEEK: “On the Setal Pattern of Caterpillars”. I]. (Communicated by Prof. J. F. VAN 
BEMMELEN), p. 1156. 
H. ZWAARDEMAKER: “Distance-relations in the Effects of Radium-radiation on the isolated Heart”, 
p. 1161. 
U. P. v. AMEIJDEN: “The influence of light- and gravitational stimuli on the seedlings of Avena 
sativa, when free oxygen is wholly or partially removed”. (Communicated by Prof. F. A. F. C. 
WENT) p. 1165. 
S. W. VISSER: “On the diffraction of the light in the formation of halos”. (Communicated by Prof. 
J. P. KUENEN), p. 1174. 
F. A. H. SCHREINEMAKERS: “In-, mono- and divariant equilibria”. XVI, p. 1196 and XVII, p. 1205. 
W. DE SITTER: “On the relativity of inertia. Remarks concerning EINSTEIN’s latest hypothesis” 
p. 1217. 
J. WOLTJER Jr.: “On the Theory of Hyperion, one of Saturn's Satellites”. (Communicated by Prof. 
W. DE SITTER), p. 1225. 
E. H. BiiCHNER and ADA PRINS: “Vapour pressures in the system: carbon disulphide-methylalcohol.” 
(Communicated by Prof. A. F. HOLLEMAN), p. 1232. 
F. ROELS: “Intercomparison of some results obtained in the Investigation of Memory by the Natural 
and the Experimental Learning-Method”. (Communicated by Prof. C. WINKLER), p. 1242. 
H. C. DELSMAN: “On the relation of the anus to the blastopore and on the origin of the tail in 
vertebrates”. (Communicated by Prof. J. BOEKE), p. 1256. (With one plate). 
M. W. BEIJERINCK: “The Enzyme Theory of Heredity’, p. 1275. 
L. S. ORNSTEIN and F. ZERNIKE: “Contributions to the kinetic theory of solids. I. The thermal 
pressure of isotropic solids.” (Communicated by Prof. H. A, LORENTZ), p. 1289. 
L. S. ORNSTEIN and F. ZERNIKE: “Ibid. II. The unimpeded spreading of heat even in case of devia- 
tions from HOOKE's law”. (Communicated by Prof. H. A. LORENTZ), p. 1295. 
12 
Proceedings Royal Acad. Amsterdam. Vol. XIX. 
