XX CONTENTS 



WoLTJEK (H. R.) and H. Kamerlingh Onnës. Further experiments with 

 liquid helium. T. Magnetic researches. XXIII. On the magnetisation of 

 gadolinium sulphate at temperatures obtainable with liquid helium. 626. 



Women, Dutch {The menarche in) and its precipitated appearance in the 

 youngest generation. 650. 



WlJHE (J. W. van). Thymus, spiracular sense organ and fenestra vestibuli 

 (ovalis) in a 63 m.m. long embryo of Heptanchus cinereus. 727. 



Zand E (Mrss J. E. van der) and B. Sjollema. Researches on the 

 metabolism of milch-cows suffering from acetonemia. 666. 



Zeeman (P.) and H. W. J. Dik. A relation between the spectra of ionized 

 potassium and argon. (Second comm.). 498. 



Zoology. H. BoscHMA : "Experimental budding in Fungia fungites." 88. 



— G. J. VAN OoRDT: "Secondary sex-characters and testis of the ten-spined 

 Stickleback (Gasterosteus pungitius L.)." 309. 



Zwaardemaker (H.), W. E. Ringer and E. Smits. Is caesium radio-active? 



575. 

 Zwaardemaker (J. B.). The presence of cardio-regulative nerves in 



Petromyzon fluviatilis. 438. 



— and J. G. Dusser de Barenne. On the influence of the vagi on the 

 frequency of the action currents of the diaphragm during its respiratory 

 movements. 771. 



