The Cambridge natural history . iaxisamong land and fresh-water Mollusca, and Cymba and manyLittorina amongst marine. The young of Melania tuberculata,in Algeria, have been noticed to return, as if for shelter, to thebranchial cavity of the mother, some days after first quitting species among Pulmonata are known to be ovovivi-parous, Patula Cooperi, P. Hemphilli, and P. rupestris,Acanthinula liarpa, Micro;p]iysa vortex, Pupa cylindracea andviuscorum, Clausilia ventricosa, Opeas dominicensis, Rhytida in-aequalis, etc. All fresh-water Pelecypoda yet examined, exceptDreissensia,
The Cambridge natural history . iaxisamong land and fresh-water Mollusca, and Cymba and manyLittorina amongst marine. The young of Melania tuberculata,in Algeria, have been noticed to return, as if for shelter, to thebranchial cavity of the mother, some days after first quitting species among Pulmonata are known to be ovovivi-parous, Patula Cooperi, P. Hemphilli, and P. rupestris,Acanthinula liarpa, Micro;p]iysa vortex, Pupa cylindracea andviuscorum, Clausilia ventricosa, Opeas dominicensis, Rhytida in-aequalis, etc. All fresh-water Pelecypoda yet examined, exceptDreissensia, are ovoviviparous. The number of eggs varies greatly, being highest in thePelecypoda. In Ostrea cdulis it has been estimated at from300,000 to 60,000,000; in Anodonta from 14,000 to 20,000;in Unio lyictoruni 200,000. The eggs of icons are reckoned atfrom 80,000 to 600,000, oi Loligo and Sepia at about 30,000to 40,000. Pulmonata lay comparatively few eggs. Arion aterhas been observed to lay 477 in forty-eight days (p. 42). Kests. I 24 EGGS OF LAND PULMONATA chap. of Helix aspersa have been noticed, in which the ninnber of eggsvaried from about 40 to 100. They are laid in little cup-shaped hollows at the roots of grass, with a little loose earthspread over them. The eggs of TcstaccUa are rather large, andvery elastic; if dropped on a stone floor they will rel)Oundsharply several inches. The Coclilostyla of the Philippines laytheir eggs at the tops of the great forest trees, folding a leaftogether to serve as a protection. The eo-Q-s of the ureat troincal Bulimus and Acliatina,together with those of the Macroongroup of Helix {Helicoplianta^ Acarvs,Ianda) are exceedingly large, and theiiunil)er laid must be decidedly lessthan in tlie smaller Pulmonata. Buli-iiius ohlonr/vs, for instance, from Bar-1 )ados, lays an egg about the size of a si)arrows (Fig. 38), Acliatina sinis-Fio. 38.—Xewly-hatched youiiEf / \ ^ ^ . , ^. and egg oi Bubmns obhngus tiovsa as large as a pigeons. Ihe Mi
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
