REPRODUCTION gi 
a similar habit. Among these “ incubatory ” forms- 
is Calyptr@a Chinensis, whose egg capsules are retained 
between the foot of the parent and the object to 
which it is attached. Vermetus retains them within 
the mouth of the shell. The female Argonaut 
secretes and carries about a shell as already described 
(ante, p. 40) solely for their protection. Her eggs, 
in a granulated mass attached to a many-branched 
stem, are retained in the spire of this nidamental 
shell. Another Cuttlefish (Polypus Digueti) on the 
Californian coast, failing a shell of its own, makes 
use of the empty tenement of a large Bivalve. In 
this it establishes itself, facing outwards from the 
hinge, and by means of its arms opens and closes 
the shell at will. It deposits its eggs round about in 
the under valve, and the young, as they successively 
hatch out, swarm about and crawl over the parent, 
who remains ready to shut the shell at the first sign 
of danger. 
Certain small Land Snails belonging to the group 
Libera of the genus Endodonta, met with in the 
Antipodes, deposit their eggs in the umbilicus of the 
shell, sealing the opening with a thin, sometimes 
shelly, epiphragm, through which on hatching the 
young perforate their way. 
In some species of Melania, Spekia, and Tanganyicia, 
the embryos develop in a special brood-pouch formed 
by an infolding of the skin near the right tentacle. 
It is among the Bivalves, however, that the most 
