[7] INSTRUCTIONS FOR COLLECTING MOLLUSKS BALL. 



selves to the bark of trees or to stones for a period of hibernation. 

 They close the aperture of the shell with a leathery secretion, some- 

 times strengthened by more or less limy matter, or if naked may sur- 

 round themselves with it like a cocoon. This temporary defense, 

 common to most of the inoperculate forms, is called the epiphragm, 

 and, in the many whorled species, there are often several of these par- 

 titions between the retracted animal and the aperture of its shell. In 

 the arboreal Bulimi the secretion is often of great strength, and the 

 collector who finds them fastened to trees and attemjDts to pull them 

 off will often see the shell or the bark break before the epiphragm will 

 give way. In such cases it is better to cut off a thin slice of the bark 

 with the adherent shell. On an immersion in warm water the mollusk 

 will awake and soon release itself in the natural way. It is the habit 

 of many snails on waking from their hibernation to make their first re- 

 past on their own epiphragm. The period of attachment is often 

 marked by a band of color in harmony with the lines of growth, not 

 elsewhere repeated on the shell, and usually bluish or dark brown. 

 This indicates the formation of a special secretion at such times. The 

 life of most land shells is probably short, a majority probably do not 

 live more than a year or two, though, under suitable conditions, there 

 would seem to be no reason why this period should nob be much pro- 

 longed. The species of arid regions become accustomed to long periods 

 of enforced hibernation and are the longest lived. Instances are known 

 of their surviving four or five years without food in this state, and it is 

 a common thing for them to survive transportation through long sea 

 voyages to distant countries. These facts have an important bearing 

 on their distribution. There would seem to be no doubt that in some 

 cases the ancestors of a land shell fauna have reached oceanic islets by 

 drifting on vegetation dislodged by freshets and carried out to sea, 

 especially in the warmer regions. 



COLLECTma OUTFIT. 



The collector of land shells needs only a very simj^le and inexpensive 

 outfit. For most purposes, in temperate and northern regions, the 

 things needed may be easily carried in one's x)ocket. First in point of 

 usefulness is a pair of spring forceps, which should have a delicate spring 

 requiring no sensible exertion to make the points meet. The points 

 themselves should be slender and the file cutting on their inner sides 

 should not be coarse. These forceps, which any surgical instrument 

 maker should furnish at a cost of $1 or less, are indispensable in col- 

 lecting the more minute forms, for which the fingers are far too clumsy. 

 After a little practice the most minute Vertigo or Hyalinia may be 

 picked up without injury, though the beginner is apt to crush a goodly 

 number before he learns the necessary dehcacy of manipulation. The 

 forceps come into play almost as much in separating the day's collec- 

 tions as in making them 5 in fact, after a little, one feels lost without 

 them. 



