14 THE NAUTILUS. 



burrow in the soil ; in every cnse the aperture of the shell is upward, 

 with the apex below. With its mucus the Helix securely glues this 

 aperture to the under surface of any substance to which it attaches 

 itself. These land snails, being non-operculated pulmonates, their 

 apertures are covered by an epiphragm. (In experimenting on a 

 number of Helix tudiculata and Helix traski, my experience has been 

 that if the epiphragm has been badly punctured, or broken, the snail 

 will die unless circulation is started by applying moisture.) This 

 covering is composed of several layers of hardened mucus which 

 resembles the tougli white skin that lines a hen's egg. 



In experimenting with helices in a snailery, a wooden box covered 

 with a wire screen and partly filled with soil, I have found that 

 while one species of snail (Epiphragmophora traskii Newc.~) would 

 fasten themselves to the strip of wood that braced the lid of the 

 snailery, the other species ( Glyptostoma neivberryanuin W. G. B.} 

 would burrow in the soil, their black shells almost hidden from si<jht. 

 In order to test them I have repeatedly interrupted their aestivation 

 by placing their shells in hike-warm water until the helices could 

 crawl about, but they would eventually be found in separate places, 

 E. traski suspended above and G. newberryanum below in the soil. 



During aestivation the snail's functions are in a state of coma, 

 respiration is nearly suspended, and having retired as far as possible 

 within the shell the mollusk is the embodiment of rest. Its waking 

 is not a voluntary action. Without humidity the snail will activate 

 for months and continue in a state of torpor for years if the at- 

 mosphere is dry around it. Conchologists frequently quote the 

 example given by Dr. R. E. C. Steams, of the U. S. National 

 Museum, of a Lower Californian Helix that rested, or rather re- 

 mained in a state of torpor for six years! Other cases of prolonged 

 relaxation of the vital functions of snails are recorded. 



Some years ago, in March, 1890, I collected a few land snails 

 (E. traski Newc.) from some of the low foot-hills in Los Angeles, 

 and on reaching home, finding them glued to the glass jar, they were 

 left on a stand. In the morning two snails had crawled out of the 

 jar and up the wall and were snugly ensconced in one corner of the 

 ceiling, another one had traveled far in the night and had pre- 

 empted his claim in one corner of the hall ceiling. In order to 

 study developments they were allowed to remain -in situ. One soon 

 fell down upon the carpet but the other two remained intact. The 



