viii Contents 



The Theoretical Value of Stitherland' s Constant in the Ki-netic Theory of^ 

 Gases. By C. G. F. James, Trinity College, Cambridge. (Communi- 

 cated by Mr R. H. Fowler.) (One fig. in Text) . . . .447 



On the Stability of the Steady Motion of viscous liquid contained between 

 two rotating coaxal circidar cylinders. By W. J. Harrison, M.A., 

 Fellow of Clare College, Cambridge 455 



The soaring flight of dragon-flies. By E. H. Hankin, M.A., Sc.D., Agra, 



India. (Three figs, in Text) 460 



The Gluteal Region of Tarsius Spectrum. By A. B. Appleton. 11! 



(Plate IV) 4^^ 11 



An unusual type of mcde secondary characters in the Diptera. By C. G. 



Lamb, M.A. (Four figs, in Text) 475 



A Note on the Mouth-parts of certain Decapod Crustaceans. By L. A. 

 BoRRADAiLE, M.A., Fellow and Tutor of Selwyn College, Cambridge, 

 and Lecturer in Zoology in the University ..... 478 



An Apparatus for Projecting Spectra. By H. Hartridge . . . 480 



Note on true and apparent hermaphroditism in sea-urchins. B}' J. Gray, 



M.A., Balfour Student, Cambridge University 481 



On Certain Simply -Transitive Permutation-Groups. By Dr W. Burnside, 



Honorary Fellow of Pembroke College 482 



Proceedings at the Meetings held during the Session 1920 — 1921 . . 485 



Index to the Proceedings with references to the Transactions . . 492 



PLATES. 



Plates I— III. To illustrate Mr Waran's papers .... 48, 433 

 Plate IV. To illustrate Mr Appleton's paper 474 



CORRECTION. 



MoRDELL, p. 250, line 5, after conjugate numbers insert in the reed 

 conjugate fields. 



