PARTULA. 125 



that in both cases the sinistral snails breed truer to their type than do 

 the dextral. 



Partula otaueitana var. lignaria Garrett. 



Figs. G, 7. 



The snail represented in Fig. G is found in Tipa^rui valley. The 

 ground-color of the shell is quite similar to that of snails of color-type 5, 

 but they are distinguished from the latter by the presence of a more or less 

 distinct whorl-stripe, which extends tVom the suture of the spire through 

 the middle of the body-whorl. In a few individuals there are two separate 

 whorl-stripes, one through the middle of the body-whorl and the other 

 adjacent to the suture. These snails constitute 26.5 per cent of the fauna 

 of Tipa^rui valley. All of the specimens obtained were dextral, as were also 

 the young dissected from them. Nineteen adults yielded thirty-three 

 young, of which number twenty-eight were similar in ground-color to the 

 type of snail shown in Fig. 5, while two were as light as the snails 

 represented in Figs. 8 and 8, and three were slightly darker in color 

 than the parent shells. 



Of these young ones 41 per cent exhibit a distinct whorl-stripe, while 

 59 per cent are unstriped, and resemble in all respects the normal young of 

 snails of type 5. Indeed among the sixty-one young taken from adults 

 of type 5 in Tip^rui valley, five exhibit the whorl-stripe characteristic of 

 the young of type 6. There can be but little doubt, therefore, that in 

 type 6 we have a race of snails which is derived from type 5, and which 

 under conditions of more perfect isolation might in time develop into a 

 distinct form. It is possible that this tendency may be prevented in 

 Tipasrui valley by constant intercrossing between the adults of types 5 

 and 6. 



Fig. 7. 



The sinistral snail with two whorl-stripes, which is represented in Fig. 7, 

 is found in Hamuta and Pirse valleys, where they constitute 3 per cent 

 and 4 per cent respectively of the snail-fauna. In Hamuta valley four 

 adults yielded seven young, five of which were as light in ground-color 



