CONTENTS OF No. 218.-New Series. 



MEMOIRS : 



The Structure and Life-History of Crithidia melophagia (Flu)/*"'' J 



an Endo-parasite of the Sheep- Ked, Melophagus ovinus. By \ 



Annie Pobtek, B.Sc.Lond., Zoological Eesearch Labomtory, 

 University College, Loudon. (With Plates 12 and 13 and 15 Text- 

 figures) . . . , jgg 



Studies in the Experimental Analysis of Sex. By Geoffrey 

 Smith, Fellow of New College, Oxford. (AVith Plate 14) . . 225 



Some Observations on a Flagellate of the Genus Cercomonas. By 

 C. M. Wenton, M.B., B.S., B.Sc, Protozoologist to the London 

 School of Tropical Medicine. (With 19 Text-figures) . . 241 



Some Observations on a Xew Gregarine (Metamera schubergi 

 nov. gen., nov. spec). By H. Ltndhurst Duke, B.A., B.C. 

 Cantab. (With Plates 15 and 16) . . . . 261 



On the Anatomy of Histriobdella Homari. By Cresswell 

 Shearer, M.A., Trinity College, Cambridge. (With Plates 17— 

 20 and 5 Text-figiu-es) ..... 287 



On the Artificial Cultiu-e of Marine Plankton Organisms. By E. J. 

 Allen, D.Sc, Director of Laboratories and Secretary of the 

 Marine Biological Association, and E. W. Nelson, Assistant 

 Naturalist ..... 361 



