48 



supply of food, and various other conditions." These latter, 

 he adds, may be "permanent or local." When permanent he 

 calls them races, but, as he himself remarks, it would " be 

 difficult" to discriminate between a race and a species. 



Nov7 all this accents, with authority, the statement made 

 by me in a former paper re variability of fresh- water shells, 

 and the necessity for reduction of species ; and it clearly sup- 

 ports the course which Mr. Petterd has adopted with respect 

 to the reduction of certain species of our land shells, and 

 which all along has had my hearty concurrence. 



The result of receut investigations of Tasmanian land and 

 fresh -water shells, based upon a careful examination of large 

 numbers of individuals, of all stages of growth, from widely 

 separated localities, with varying local surroundings, geolo- 

 gical and botanical ; and taken from levels varying in some 

 cases from 1 to 4C00 feet, may be easily glanced at by passing 

 in review certain well-known typical shells and groujDing them 

 with certain varieties which have hitherto been regarded as 

 distinct species, but which according to the laws determined 

 by the consent of leading naturalists, must now, I am of 

 opinion, be considered simply as varieties of one species. 



Helix Stephens! (Cox), is perhaps within given limits the 

 most variable shell in Tasmania, in size, colour, elevation of 

 spire, and sculpture. It is also the most widely distributed, 

 and is found in varying degrees of abundance under different 

 circumstances, from sea level to a height of 4000 feet. It 

 seems to be as much at home in cold, sterile, upland regions, as 

 in the lower and more genial districts ; and I could not find 

 that its distribution was in any way affected by the geological 

 formations it was found upon, nor by the differences in vege- 

 table surroundings. 



An organism fitted to survive under such widely different 

 circumstances may be expected to vary considerably. And 

 this, in fact, is the case, for there are no less than ten species 

 created out of minute differences in character, which are most 

 unstable even in individuals from the same locality, and are 

 trifling even in the most extreme members of the group. In 

 sculpture there is a general agreement in the shell being 

 markedly cancellate ; and the form varies only to a trifling 

 extent ; but the sharpness and density of the striae, the 

 absence or presence of more or less regular and distant 

 riblets, varies with the individual at different stages of its 

 growth ; hence it is not surprising to find all the characters 

 of the ten species already referred to, melting insensibly into 



