BIOLOGICAL BULLETIN 



OF THE 



fiDartne Biological Xaborator? 



WOODS HOLE, MASS. 





VOL. LI I 



JANUARY, 1927 



No. i 



HYMAN, LIBBIE H. 



HYMAN, LIBBIE H. 



CONTENTS 



The Metabolic Gradients of Vertebrate Em- 

 bryos, III. The Chick i 



The Metabolic Gradients of Vertebrate Em- 

 bryos, IV. The Heart 39 



PRISON, THEODORE H. Experiments in Rearing Colonies of Bumble- 



Bees (Bremidce) in Artificial Nests 5 1 



BALL, GORDON H. 



Studies on Paramecium, III. The Effects 

 of Vital Dyes on Paramecium caudatum . . . 68 



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Entered October 10, tooa. at Lancaster, Pa., as second-class matter under Act of Congress of July 16 , 1894 



