THE MUSEUM. 



an external, semicareous, elastic mem- 

 brane, investing the whole, the interi- 

 or surface which is usually studded 

 with numerous rhombic, microscopic 

 crystals of carbonate of lime, some 

 species however, have a hard envelop- 

 ing calcarous shell, of the consistence 

 of that of birds egg; of an inner thin, 

 transparent and somewhat vicid fluid- 

 analogus to the albumen of bird's eggs; 

 of the albumen itself and of the vitellus, 

 which; posessing the same degree of 

 transparency as the albumen, cannot be 

 distinguished from it at this time. 

 The elastic eggs when first laid, are 

 often flascid, and seemingly only half 

 full of fluid, but they soon absorb 

 moisture and become distended. The 

 embryo animal with its shell, is ob- 

 servable in the albuminous fluid in a 

 few days after the egg is laid. It 

 hatches, under ordinary circumstanes, 

 in from 20 to 30 days according to the 

 state of the atmosphere. Warmth 

 and humidity hasten the process, 

 while cold and dryness retard it to an 

 almost indefinite extent. The hatch- 

 ing of eggs laid late in autumn is often 

 interrupted by the approach of cold 

 weather and of snow, and delayed un- 

 til the next Spring. 



The young animal gnaws its way 

 out of the egg, and makes its first re- 

 past of the shell it has just left. It 

 consists at first of about one and a half 

 whorls, the umbilicus being minute but 

 open. Its growth is rapid, and it has 

 usually increased in magnitude three 

 or four times by the end the first year. 



In the month of October, or at the 

 epoch of the first frost, the snail ceases 

 to feed, becomes inactive, and fixes it- 

 self to the under surface of the sub- 

 stance by which it is sheltered, or par- 

 tially burrows in the soil, and with the 

 aperature of the shell upwards, dis- 

 poses itself for its usual sleep or hiber- 

 nation. Withdrawing itself into the 

 shell, it forms over the aperture a 

 membranous covering, consisting of a 

 thin semi- transparent mixture of lime, 

 mucus or gelatine, secreted from the 

 collar of the animal. This membrane 



is called the epiphragm. It is formed 

 in this manner: the animal being with- 

 drawn into the shell, the collar is 

 brought to a level with the aperture, 

 and a quantity of mucous is poured 

 out from it and covers it. A small 

 quantity of air is then emitted from 

 the respiratory foramen, which de- 

 taches the mucous from the surface of 

 the collar, and projects it in a convex 

 form, like a bubble. At the same mo- 

 ment, the animal retreats further into 

 the shell, leaving a vacuum between it- 

 self and the membrane, which is con- 

 sequently pressed back by the external 

 air to a level with the aperature, or 

 even farther, so as to form a concave 

 surface, where, having become desic- 

 cated and hard, it remains fixed. 

 These operations are nearly similtan- 

 eous, and occupy but an instant. As 

 the weather becomes colder, the ani- 

 mal retires further within the shell, 

 and makes another septum, and so on, 

 until their are sometimes as many as 

 six of these partitions. The circula- 

 tion becomes slow, the pulsations of 

 the heart, which in the season of ac- 

 tivity vary from 40 to 60 in a minute, 

 according to the temperature of the 

 air, decrease in frequency and strength 

 until they at length become impercepta- 

 ble. The other functions of the body 

 cease, and a state of torpidity succeeds 

 which is interrupted only by the reviv- 

 ing heat of the next Spring's sun. 

 During the months of April and May 

 or on the accession of the first warm 

 weather of the season, the animal 

 breaks down and devours the mem- 

 braneous partitions and comes forth to 

 participate in the warmth and fresh- 

 ness of the season. At first is is weak 

 and inactive, but recovering in a short 

 time its appetite, resumes its former 

 activity." 



We will next month give a further 

 chapter on these most interesting an- 

 imals. They are to be found in all 

 parts of the U. S. and in some sections 

 but little is known of the present fauna. 

 Good results and many new species 

 will doubtless be discovered and we 



