VI 



CONTENTS 



Page 



What is the meaning of predation? by Paul L. Errington 243 



The gorillas of the I^yonsa region, Western Kigezi, SW. Uganda, by 



Capt. C. R. S. Pitman 253 



The vampire bat: A presentation of undescribed habits and review of its 



history, by Raymond L. Ditmars and Arthur M. Greenhall 277 



Some of the commoner birds of Ceylon, by Casey A. Wood 297 



The wax palms, by Miriam L. Bomhard 303 



Significance of shell structure in diatoms, by Paul S. Conger 325 



Some aspects of the plant virus problem, by Kenneth M. Smith 345 



Sun rays and plant life, by Earl S, Johnston 353 



Reactions to ultraviolet radiation, by Florence E. Meier 373 



Aerial photography, by Capt. H. K. Baisley 383 



Easter Island, Polynesia, by Henri Lavachery 391 



The Eskimo archeology of Greenland, by Therkel Mathiassen 397 



Petroglyphs of the United States, by Julian H. Steward 405 



The history of the crossbow, illustrated from specimens in the United 



States National Museum, by C. Martin Wilbur 427 



