habits of these latter creatures—terrestrial, fresh-water, and marine univalves, and Sea-Slugs.[1]
PULMONATA.
In Pulmonata, other than Land-Slugs, spinning chiefly occurs among the air-breathing fresh-water Snails, in which it is probably general. Among the Land-Snails of the order it appears to be very rare; the Helicidæ (typical Snails) are entirely unrepresented, as also, with the exception of a single genus, are all the other groups with Helicoid shells. For Pupidæ we have two notes, but these, as it appears to the writer, are in need of confirmation. With regard to the more or less Helicoid, semi-Slug-like Vitrina pellucida, one finds that Mr. Collinge several times tried, without success, to induce the creature to suspend itself;[2] and a few trials by the writer with various land-shells (which were placed on twigs of needle-furze, &c.) were also unsuccessful, the animals gliding off and falling without a thread, or retiring into their shells and remaining on the twigs. In Testacellidæ, I tried Testacella scutulum; in Vitrinidæ, Vitrina pellucida; in Helicidæ, young Helix aspersa and nemoralis (or hortensis); in Pupidæ, Clausilia laminata and C. rolphii; and in Stenogyridæ, Cochlicopa lubrica.
Zonitidæ.
According to Andrew Garrett, the mucus of Trochonanina conula,[3] and of other species of Trochonanina, is unusually tenacious, "and the animals possess the habit of 'thread-spinning' to perfection"; so much so, it is added, that it requires no small amount of patience, while gathering specimens, to detach them from the fingers, and secure them in the box or vial.[4]
- ↑ On the subject of the mucus-threads of Land-Slugs, I hope to give, in another place, details of observations and references; in addition to these molluscs, and to those now considered, the Mollusca-Pelecypoda (bivalves) are thread-makers and byssus-spinners, but I am unable at present to write of the habits of this class of Mollusca. For help in preparing the present paper, and in other tasks, I am much indebted to the courteous and continued co-operation of my friend Mr. G.K. Gude.
- ↑ Collinge, Zool. (3), xiv. (1890), p. 468.
- ↑ Microcystis conula.
- ↑ Garrett, 'Journal of the Academy of Natural Sciences of Philadelphia' (2), viii. (1881), pp. 383–4; ix. (1884), p. 21.
