XVIII CONTENT Ss. 
ZEEMAN (P.). The law of shift of the central component of a triplet in a magnetic 
field. 473. 
Zoology. G. C. J. Vosmarr: “Poterion a boring sponge”. 37. 
— P. P.C, Hoek: “Some results of the investigation of the Cirripeds collected 
during the cruise of the Dutch man-of-war “Siboga” in the Malay Archipelago”. 
110. 
— Miss Winirrep E, Cowarp: “On Ptilocodium repens a new gzymnoblastic 
hydroid epizoic on a pennatulid” 635, 
— G, C. J. Vosmaer: “On the spinispirae of Spirastrella bistellata (O.S.) Ldfd.”. 
642. ; 
ZWAARDEMAKER (H.) presents a paper of Dr. A. K. M. Noyons: “About the 
determination of hardness in muscles’. 43. 
— presents a paper of Dr. A. K. M. Noyons: ‘About the independence of the 
electrocardiogram with regard to the form-cardiogram”. 273. 
— presents a paper of Dr, A. K. M. Noyons: “About observations on the electro- 
myogram and form-myogram under the influence of fatigue.” 723. 
