REPRODUCTION 91 



a similar habit. Among these " incubatory " forms 

 is Calyptrcea Chinensis, whose egg capsules are retained 

 between the foot of the parent and the object to 

 which it is attached. Vevmetus 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 



