IN A SNAILERY. 15 
The pulmonates unite both sexes in one individual, but 
it requires the mutual union of two individuals to fertilize 
the eggs. The eggs are laid in May or June, when large 
numbers of snails gather in sunny places. When about to 
lay, the snail burrows into damp soil or decaying leaves, 
underneath a log, or in some other spot sheltered from the 
sun’s rays, and there drops a cluster of thirty to fifty eggs 
looking like homeopathic pills. Three or four such de- 
posits are made, and abandoned. This is the ordinary 
method of the genus helix, but some of the land and all 
the pond-snails present variations. The ova of slugs are 
attached by the ends in strings, like a rosary, and many de- 
posits are made during the year. Bulimus and other South 
American genera isolate each egg, which in the case of some 
of the largest species is as big as a pigeon’s. Vitrina and 
succinea glue them in masses upon stones and the stems of 
plants, while the tropical bulimi cement the leaves of trees 
together to form nests for their progeny. The pond-snails 
hang little globules of transparent gelatine containing a few 
eggs, or otherwise secure their fry to wet stones, floating 
chips, and the leaves of aquatic plants. In neritina, a brack- 
ish water inhabitant, the ova, immediately upon being laid, 
become attached to the surface of the parent’s shell, and 
when the embryo hatches each egg splits about the middle, 
