VOL. XII, NO. 484 



APEIL, 1907 



THE 



AMERICAN 

 NATURALIST 



A MONTHLY JOURNAL 

 DEVOTED TO THE NATURAL SCIENCES 

 IN THEIR WIDEST SENSE 



CONTENTS 



The Geographic Distribution of Closely Belated Species 



DR. ROBEBT GREENLEAF LEAVITT 

 The Coincident Distribution of Belated Species of Pelagic OrganiBms as Illus- 

 trated by the Chaetognatha . . PBOF. CHARLES ATWOOD KOFOID 

 The Attached Young of the Crayfish Cambarus clarkii and Cambarus 



and Mutualism ; Geology, Relative Geological Importance c 

 nental, Littoral, and Marine Sedimentation, Obser%'ations in South 

 Africa, Geology of the Big Horn Mountains, A Glacial Lake in Tibet ; 

 Zoology. A Statue of Lamarck, Gardiner's Maldive and Laccadive 

 Archipelagoes, Kolhnann's Atlas of Human Embryology, The System- 

 atic Position of the Tubinares, Beebe's The Bird, The Conus Arteriosus 

 in Teleosts, Does half of an Ascidian Egg give rise to a whole Lar\'a ? 

 Digestive processes in CoUembola, Fresh Water Amphipods of North 

 America, Some Problematic Worms; Botany. Sukkulente Euphorbien 276 



BOSTON, U. S. A. 

 GINN & COMPANY, PUBLISHERS 

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