THE VARIATIONS AND MUTATIONS OF THE 

 INTRODUCED LITTORINA. 



A THIRD CONTRIBUTION TO THE STUDY OF VARIATION. 



HERMON C. BUMPUS. 



THE observations recorded in this communication were made 

 for the purpose of ascertaining additional facts relative to the 

 variability of "introduced species," and with the design of 

 eliciting further evidence in corroboration of certain conclu- 

 sions which had been reached after an examination of a large 

 number of eggs of the English sparrow (Bumpus, '98). 



The periwinkle, Littorina littorea Linne, is " extremely 

 common ' among stones and on the rocks of the British 

 shores, and is reported from Greenland, the White Sea, and 

 the European coast as far south as Lisbon (Jeffreys, '65). 

 Along the New England shore it is by far the most abundant 

 mollusc at the present time. Stones, piles, and seaweed are 

 everywhere dotted with the dark-colored shells which often 

 form a distinct band near high-water mark. 



When the tide is low, the snails often lose their hold and 

 roll from the slanting rocks into hollows, where they may be 

 scooped up by the handful. At Seaconnet no less than 2500 

 shells were taken from a small depression not more than a 

 foot square. 



The history of the introduction and distribution is as 

 follows : 



In 1841 Gould published his Report on tJie Invertebrate 

 Animals of Massachusetts, but no mention was made of the 

 present species. 



In 1855 Morse received specimens from Bathurst, on the 

 Bay of Chaleur, an inlet of the Gulf of St. Lawrence (Morse, 

 1880). 



In 1870 Binney revised Gould's Report, gave a description of 

 the species, and mentioned the shell as reported from Halifax 



