REPRODUCTION OF LOST PARTS. 
383 
nourished by the secretions of the brood pouch, within which they 
may remain, as in the Sphceriidcv, until they are fully one-third the 
size of the parent shell. 
In the although the earlier phases of their development 
are passed through within the gill-cavities of the parent, the larvte 
upon exclusion adopt a parasitic life, fixing 
themselves upon the fins or gills of fishes 
and becoming encysted thereon by a patho- 
logical development of the tissues of the 
host, but are so different from the adult 
animal that they were formerly described 
as independent parasitic organisms under 
the name of Gloclildium parasiticimi, and it is only after a secondary 
metamorphosis, undergone during encystment, that they assume the 
adult form. 
Experiments have demonstrated the power of mollusks to reproduce 
or renew the mantle, the foot, the tentacles, or even the head when 
these have become injured or separated by accident or design, but it 
is essential that the cerebral ganglia should not have sustained serious 
injury. Certain extra-British species are known to spontaneously and 
voluntarily cast off the hinder part of the foot when in danger, taking 
advantage of the circumstance to escape. 
LITERATURE. 
(Additional to the works enumerated on page 131 et seq.)- 
Adams, L. E. — Observations on tlie Pairing of Liniax maximus L. — Jonrn. 
of Conch., July, 1898. 
Ashford, C. — On the Action of tlie Heart in the Helicidie during Hiberna- 
tion. — Journ. of Conch., April, 1882. 
The Darts of British Helicidm. — Journ. of Conch., 188.3-1884. 
Balfour, F. M. — A Treatise on Comparative Embryology. — London, 1880. 
Bell, F. Jeffrey. — Comparative Anatomy and Pliysiology. — London, 1885. 
Bernard, Felix. — Rechercbes sur les Organes Palle;iu.x des Gasteropodes 
Prosobranches. — An. d. Sci. Nat., 1890, pp. 89—401, and 10 plates. 
Binney, W. G. — On the .Jaw and Lingual Membrane of North American 
Terrestrial Pulmonata. — Proc. Ac. Nat. Sci., Philad., 1875. 
The Terrestrial Air-breathing Mollusks of the United States and the 
adjacent territories of North America. — Cambridge, July, 1878. 
Boas, J. E. V. — Text Book of Zoology, translated by J. W. Kirkaldy and 
E. C. Pollard, London, 1896. 
Bonney, T. G. — On tlie Supposed Occurrence of Pliolas burrows in the 
upper part of the Great Orme’s Head. — Geol. Mag., 1869, pp. 483 — 9, 
and pi. xvii. 
Bouchard-Chantereaux — Catalogue des Mollusques terrestres et Iluviatiles 
* * dans le departenient due Pas-de Calais. — Boulogne, 1838. 
Bowell, E. W.W. — The Odontophores of Mollusca. — Sci. Goss., June, 1897. 
Fig. 721. — Embryos of Unio, 
encysted upon the gills of a 
Perch, greatly enlarged (after 
Pelseneer). 
