100 PARTULINA, SECTION BALDWINIA. 



shells from some cause are unable to find the way back to the 

 tree on which they were born though but a few feet distant. 

 A favorite resting place of the Achatinellas is on the under 

 side of leaves, especially dead leaves, and as these fall or are 

 blown off by high winds they naturally carry the shells with 

 them usually to the ground immediately beneath the tree. 

 In a number of instances shells that had shaken from the 

 tree into the grass from six to twelve feet away from the 

 trunk were found where they had fallen several weeks later, 

 being apparently quite lost. That Achatinellas can travel 

 twelve or fifteen feet over a tree in a single night there can 

 be no doubt, since the author has observed them in the act 

 and has measured the distance traveled; no doubt they arc 

 able to travel much farther than this, as certainly can the 

 Amastras and the apparently still weaker Succineas. It 

 seems likely, therefore, that natural sluggishness or defective 

 vision, perhaps both, are responsible for the failure of such 

 shells as fall or are blown from trees to find their way back 

 to the parent trunk. "Whatever the explanation, the fact that 

 the three species of Achatinellas here considered are as a 

 rule very sedentary and rarely or never regain their place on 

 a particular tree when once dislodged seems to the author in- 

 disputable. 



" The question then arises as to the means of dispersal 

 from tree to tree and from locality to locality possessed by 

 shells under 'Conditions similar to those here indicated. The 

 author is convinced that the dispersal of the three species 

 here mentioned is effected chiefly through the agency of wind 

 when the shells are young. In several instances he has found a 

 single young Partulina, but a few days old, to be the sole oc- 

 'Cupant of a shrub or tree (so small as to be readily examined 

 leaf by leaf) separated several hundred yards from the near- 

 est shell-bearing trees. In such cases no other transporting 

 agency suggests itself but the wind or birds. 



" It would require a considerable gale to carry to a dis- 

 tance a leaf laden with an adult Acliatinella, but a very mod- 

 erate wind would suffice to <carry a leaf with a young one 

 which weighs but a gramme or two for a considerable dis- 



