No. 2.] SNAILS OF THE GENUS 10— ADAMS. 85 



This may be compared with the change of dominance with age, but in the case of secondary 

 sexual characters castration may be able to change or prevent the development or expression 

 of the adult characters. Furthermore females occasionally develop male characters and thus 

 both sexes may show latent or unexpressed characters which vary with age. The castration 

 which may influence the dominance of one sex may be compared with the influences of the 

 dominant smooth shell in the cross which leads to inversion. It is of further interest that such 

 sex characters, and even sex itself, appears to be inherited in some animals in Mendelian fashion 

 (cf. Morgan. Amer. Nat., vol. 45, 1911, pp. 65-78). In lo undulations, low and long spines, 

 show inverse development in many degrees, apparently depending on the degree of amount 

 or intensity of the character. The vast amount of diversity and variation in these shells, from 

 this point of view, may be looked upon as due to the numerous strains and their combinations 

 in different degrees of intensity, made possible by the environment, and supplemented by the 

 fluctuations which are due to the influence of the local environments, not only upon the body 

 but also possibly upon the germ. This is a condition similar in many respects to the complex 

 mixtures or strains seen in those domestic animals which are of multiple origin from diverse 

 races (cf. Ewart. The Principles of Breeding and the Origin of Domesticated Breeds of Animals. 

 Twenty-seventh Ann. Rep. Bureau of Animal Industry, U. S. Dept. Agric. (1910), pp. 125-186, 

 1912). 



ACKNOWLEDGMENTS. 



During the prosecution of this study aid, cooperation, and suggestions have come from 

 many and diverse sources, and I gladly take this opportunity to express my indebtedness to 

 them. 



To the American Association for the Advancement of Science I am indebted for grants 

 amounting to $300, and to the board of directors of the Bache fund of the National Academy 

 of Science for a grant of $125. 



To Dr. C B. Davenport, formerly of the University of Chicago, and now director of the 

 station of experimental evolution, of the Carnegie Institution of Washington, Cold Spring Har- 

 bor, N. Y., under whose general direction this investigation was begun, for his permission and 

 encouragement to take up such a subject as the present one. This was at a time when very 

 little encouragement was given to such studies by any of our larger universities, and I have sin- 

 cerely appreciated this freedom and his very valuable assistance. 



To Dr. W. H. Dall, of the Smithsonian Institution, I am indebted for many favors. 



To Dr. C. W. Hayes, formerly chief geologist, United States Geological Survey, I am in- 

 debted for suggestions concerning the physiographic history of the Southern Appalachians. 



To Dr. R. E. Call, Mr. Charles W. Johnson, Mr. Charles T. Simpson, Mr. A. A. Hinkley, 

 the late Mrs. George Andrews, and Mr. Frank C. Baker I am also indebted for numerous favors 

 and information concerning these shells. Mrs. Andrews kindly loaned numerous shells. 



To my friends, Messrs. the late Joseph and J. J. Thompson and families, of Springvale, 

 Tenn., I am indebted for cooperation and hospitahty; to Mr. N. F. Blevins, of St. Paul, Va., 

 my helper in the field, for his efficient and faithful services; and to a large number of collectors 

 who have aided me in securing shells, all of whom are mentioned with the data concerning the 

 collections. I sincerely appreciate the efficient help derived from these persons. 



To Messrs. W. B. Bevill, C. P. Gaither, of the Norfolk & Western Railway, and J. L. Meek, 

 of the Southern Railway for courtesies and for cooperation of agents along their respective 

 lines. 



To Mr. and Mrs. Ethan Viall, Mr. F. P. Pritchard, and Mr. A. G. Stillhamer I am indebted 

 for assistance. To my sister. Miss Katharine K. Adams, I am indebted for a large amount of 

 help in the calculations, and for numerous verifications, as well as much other valuable assist- 

 ance. To my wife,. AHce Norton Adams, I am also indebted for much valuable assistance. 



The photographs have been made by several persons. The work by Mr. F. M. Woodruff, 

 of the Chicago Academy of Science, has been cooperative, and also expresses the progressive 

 policy of the curator, Mr. Frank C. Baker. 



