442 PROCEEDINGS OF THE AMERICAN ACADEMY, 



4. Two " Stages " appear to be represented by the iudividuals meas- 

 ured. Many of the curves are compound, and it is probable that in these 

 one mode represents those individuals which have recently molted, the 

 other those which are almost ready for the process. 



5. All the measurements are larger on the side of the great chela. 



6. The results of this study in variation seem to indicate that right- 

 and left-haudedness is not directly due to heredity, but is caused by 

 certain slight variations which give one side of the body an advantage 

 over the other. 



Bibliography. 

 Bateson, "W. 



'94. Materials for the Study of Variation treated with special Regard 

 to Discontinuity in the Origin of Species. Loudon and New 

 York, Macmillan & Company. 608 pp. 

 Davenport, C. B. 



'99. The Importance of Establishing Specific Place-Modes. Science, 

 N.S., Vol. 9, No. 220, pp. 415-41G. 

 Davenport, C. B. 



'99". Statistical Methods with special Reference to Biological Variation. 

 59 pp., 10 tables, and 28 figs. New York, John Wiley & Sons. 

 "Weldon, W. F. R. 



'93. On Certain Correlated Variations in Carcinus maenas. Proc. Roy. 

 See. London, Vol. 54, pp. 318-329. 



