BIOLOGICAL BULLETIN 



OF THE 



flDarine Biological Xaborators 



WOODS HOLE, MASS. 



Vol. XLIV 



February, 1923 



No. 2 



Lillie, Frank R. 

 Glaser, Otto. 



Supplementary Notes on Twins in Cattle ... 47 

 Copper, Enzymes, and Fertilization .... 79 



/£% 





FEB 13 1923 





Published Monthly by the 



MARINE BIOLOGICAL LABORATORY 



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THE NEW ERA PRINTING COMPANY, Inc. 

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Single Numbers, 75 Cents. Per Volume (6 numbers), S3.00 



Entered October 10, 1902, at Lancaster, Pa., as second-class matter under Act of Congress of July 16, 1894. 



