18 Moll. 
MOLLUSCA. 
regarded as one (and not the least) of the causes which effect the unsym- 
metrical spirality of most gastropod shells. P. Am. Ass. 29th Meeting, 
Boston, 1880 (Salem: 1881), pp. 527-550, pis. i. & ii. Some critical 
remarks by W. Dall, Am. Nat. xvi. p. 878. 
II. Guajjau has published his researches on the spiral lino of the shells 
[Zool. Ree. xviii. Moll. p. 15] in a special volume (title supra). 
General notes on sinistral embryonal shells by Jousseaum e ; Le Nat. 
1882, p. 158. 
10 . Biology. 
Note on the duration of life in some Mollusca : Vitrina lives only 1 
year ; Cyclas and Pisidium 2, Hyalina , Succinea , Limn<ea ) Planorbis , and 
Ancylus are full-grown in 2-3 years; Helix and Paluclina 2-4; Pupa , 
Bulimus , and Clausilia are full-grown in 2 years, but live probably 
longer as adult shells, and are much more plentiful than young ones ; 
Anodonta in about 12-14. Clessin in Weissmann’s Ueber die Dauer des 
Lebens, 1882, pp. 79-81. 
C. Ashford makes some very interesting observations on the hiberna- 
tion of snails : — Helix pomatia, nemoralis , aspersa , and arbustorum 
hibernate completely, retiring once for all for the winter in England ; 
Vitrina pellucida , Helix fusca , sericea , caperati , hispida , pulchella , 
hortensis , ru/escens ; Zonites cellarius and alliarius ; Cochlicopa lubrica 
and Bulimus acutus , on the contrary, can be found moving aud feeding 
in December, January, and February. The author observed the pulse of 
Helix hortensis and Zonites cellarius in hibernation during the three 
winter months, and found that its frequency decreased with the tem- 
perature, being 12-14 per minute at 42-44° Fahr., 9-11 at 37-38° Fahr., 
4-8 at 2G-33° Fahr. ; at the lower temperatures, not only the contrac- 
tions of the heart are reduced to few in number, but are also irregular, 
a full and deliberate contraction being followed by one, two, or three, 
of very small amplitude. The epiphragm of Helix hortensis was always 
opaque and papyraceous below or near freezing point, otherwise thin 
and pellucid ; it was destroyed and renewed five times during the three 
months. Zonites cellarius formed no epiphragm, and a part of the body 
was outside the aperture during the whole of the three months. J. of 
Conch, iii. pp. 321-326. 
Rouzaud has proved that land-snails not only absorb water by the 
surface of the foot, but also swallow a considerable quantity by the 
mouth ; he thinks that the mucous cover of the body protects them 
against too much evaporation of water. C. R. Assoc. Fran£., 9 me sess. 
Reims, 1880 (Paris, 1881) pp. 713-715. 
Jousseaume makes general remarks concerning the growth of shells 
and the character of the embryonal whorls in them ; Le Nat. 1882, 
pp. 158, 159, 182, & 183. 
Increase of number, size, and form of the teeth in the radula by age in 
Hyalina cellaria (Mull.), drapurnaldi (Beck), and glabra (Stud.), statod 
by Sterki, Nachr. mal. Ges. 1882, pp. 172-178; and in several species of 
Limax by B. Esmark, N. Mag. Naturv. xxvii. pp. 92-96, figs. 3-5. 
