As an excellent general type of the nervous system, attention may be directed to that of Paludina drawn in fig.
Dium or olfactory Yet in some Pectinibranchia (Paludina) organ).
- Nervous system of Paludina as a type of the streptoneurous condition.
Paludina, Purpura, Nassa, Vermetus, Neritina.
26 the early stages of Paludina vivipara are represented.
Many Gastropoda deposit their eggs, after fertilization, enclosed in capsules; others, as Paludina, are viviparous; others, again, as the Zygobranchia, agree with the Lamellibranch Conchifera (the bivalves) in having simple exits for the ova without glandular walls, and therefore discharge their eggs unenclosed in capsules freely into the sea-water; such unencapsuled eggs are merely enclosed each in its own delicate chorion.
- Developmentof the River-Snail, Paludina, vivipara.
Accessory organs are rarely found on the genital ducts, but occur in Paludina, Cyclostoma, Naticidae, Calyptraeidae, &c. Mandibles usually present.
In the marine Streptoneura they are ectodermic projections which ultimately fall off; in the Opisthobranchs they are closed pouches; in Paludina and Bithynia they are canals as in Pulmonata.
Paludina and Bithynia are both British genera.
In Paludina the whorls of the spiral are very prominent; the genus is viviparous.
Paul similarly demonstrated genetic series of Paludina (Vivipara) in the Pliocene lakes of Slavonia (1875).
- Development of the River-Snail, Paludina vivipara.