100 
conjecture that they vary in the times of attaining 
their maturity and in the length of their lives. 
Of the mollusca, little more is known. Bingley 
relates two stories of snails, some of which revived 
after an interval of fifteen years, during which they 
had been kept as dried specimens in a museum: 
others survived after immersion in scalding water. 
Observations on the vitality of gold-fish snails, and 
others of the lower classes of animals, might easily 
be made, and probably would be made, were it pro- 
bable that the knowledge would tend to pecuniary 
or other profit. Yet it has never been tried whether 
the purpura might not be bred in pans of salt water, 
yielding the famed Tyrian dye, at small expense. 
Large snails, the helix pomatia, are bred in Germany 
for the table; but probably the quick demand for 
the delicacy may prevent observation upon the pe- 
riods of their growth, and on the natural duration 
of their lives. 
Most mature insects perish every winter, leaving 
their progeny in the egg or grub or pupa state. Yet 
some may be found torpid in light soil and heaps of 
rotten vegetables. Mole-crickets burrow during the 
winter. Some, after leaving the grub state, attain 
maturity, breed, and die in a day, as the ephemere. 
Of plants, it is well known, some are annuals, 
some biennials, some triennials, some perennials. It 
may suffice to refer generally for instances to Mawe's 
or Loudon’s Calendars. Pliny speaks of oaks in the 
Hercynian forest coeval with the world. Mons. 
Decandolles, in his Flore Francoise, says, ‘“ Mons. 
