46 



An example of divergent morphs occupying areas in close 

 proximity is illustrated in Plates xxii and xl. Both of these 

 inhabit areas on the west side of San Juan Island. Morph 25 is 

 located about one mile south of Mitchell's Bay in the northern 

 section of the coastline, and it will be noted the shells are 

 heavily corrugated with both spiral and vertical sculpture, 

 only a few individuals showing any indication of coloration. 

 The lip is devoid of dentiform nodules. In Morph 7, located 

 at False Bay, about five miles to the southward, we find a 

 population of a sharply contrasting type. Both spiral and 

 vertical sculpture are reduced to a minimum. The shells are 

 uniformly tinged with a delicate brown coloration, the angle of 

 the spire is less pronounced and conspicuous dentiform tuber- 

 cles are present on the lip. A third population, Morph 24, 

 inhabits an area at Deadman's Bay, which is located about 

 halfway betweeen the above, is of a mixed type, presenting an 

 intergrading series or cline, showing a transition between the 

 two extreme forms. Many additional examples could be cited. 

 Even the group of small islands known as the Wasps, lying 

 between Orcas and Shaw Islands, possess in each case charac- 

 teristic Thais populations. 



In the second category, of closely similar types appearing 

 at distant points, we also have numerous examples. The ap- 

 pearance of colorless forms, or those exhibiting various types 

 of banding, appear in many populations throughout the entire 

 range of the species. The proportional representation of the 

 several variations in color vary from one population to another. 

 In many cases there is a complete gradation from pure white 

 to dark brown, in others the pale forms are nearly or complete- 

 ly dominant. Again the pale forms may be much in the minori- 

 ty. The writer has seen no indication that these variations in 

 coloration are in any respect related to environmental influ- 

 ences, and regards them as primarily of genetic origin. 



The populations of Thaisy although they are extremely var- 

 ied and heterogeneous in characacter, nevertheless show indi- 

 cations of groupings that are presumably related to the early 



