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The coloration of Thais lametlosa exhibits a very wide range. 

 Many populations are completely devoid of color when the 

 scum of organic matter commonly present on the shells is re- 

 moved. A tinge of yellow, or a banded condition in this color, 

 is not infrequent. The majority of the color markings are in 

 various shades of brown, ranging from pale mahogany to dark 

 chocolate; these occur both solid and in various types of band- 

 ing. The bands may be pale on a dark background, or dark 

 on a pale background. In some populations the banding is 

 quite uniform throughout; more commonly a graded series is 

 found, ranging through pale colored forms to those that arc 

 heavily pigmented, constituting a dine within the population 

 as regards coloration . 



The problem of coloration in Thais has given rise to consider- 

 able differences of opinion. Colton as has been noted, ascribed 

 divergencies in color largely to selective agencies in the envi- 

 ronment, while Moore has presented evidence leading to the 

 conclusion that coloration in the snails is related to nutritive 

 conditions affecting the metabolism of the animals. 



The detailed and carefully controlled experiments conducted 

 by Dr. Moore cannot be lightly set aside, but some of the 

 results seem out of line with the conclusions, such as the 

 failure of pale colored snails to develop pigmentation after 

 an exposure to an exclusively Mytilus diet for a period of 

 six months; likewise the occurrence of pale individuals in the 

 midst of otherwise pigmented colonies. The failure of the yel- 

 low pigment, which belongs in the same group of carotenoid 

 compounds as the brown coloring matter, to respond to diet- 

 ary changes, is very suggestive. 



In the opinion of the writer, based however upon purely 

 observational data, the color patterns found in the local races 

 oi Thais lamellosa are genetically determined. The local popu- 

 lations, founded as they presumably were by chance migrants 

 from established colonies, carrying elements of the highly vari- 

 able ancestral stock, would eventually form inbred popula- 

 tions with distinctive characteristics. 



