No. 5.] THE INTRODUCED LITTORINA. 259 



Conclusion. 



We may then conclude that the periwinkle, subjected to a 

 new environment, and presumably emancipated from many of 

 the restraining influences of natural selection, has become in 

 any and in all American localities : 



I and II. More variable in its stature. 



III. More variable in its course of growth. 



IV. More variable in weight. 

 V. More variable in bulk. 



VI. More variable in the limitations and boundaries of the 

 color patterns. 



While presenting these extremes of variation, the American 

 type of Littorina littorea, when compared with the European 

 type, is more elongated, lighter in weight, more bulky, and the 

 color markings are less pronounced. 



These results are in harmony with and fully corroborative of 

 the conclusions reached from the statistical study of the 

 sparrow's egg. 



UNIVERSITY, PROVIDENCE, R. I. 

 September 10, 1897. 



BIBLIOGRAPHY. 



'41. GOULD, A. A. A Report on the luvertebrata of Massachusetts. 



Cambridge. 



'65. JEFFREYS, J. G. British Conchology. London. 

 '70. BIXNEY, W. G. Report on the Invertebrata of Massachusetts. 2d 



ed. Boston. 



79. GRAY, A. F. Science News. April 15. 



'80. VERRILL, A. E. Note in Silliniarfs Journal. September, 1880. 

 '80. MORSE, E. S. The Gradual Dispersion of Certain Mollusks in New 



England. Bull. Essc.v I nst. Vol. XII. 

 '98. BuMi'Us, H. C. The Variations and Mutations of the Introduced 



Sparrow. (A Second Contribution to the Study of Variation.) 



Biological Lectures. Woods Holl. 1897. 



