ANATOMY AND PHYSIOLOGY. 
Moll. 19 
9. The Shell Generally. 
H. L. Osborn has inserted pieces of glass between the outside of the 
mantle and the inside of the shell of living oysters, and studied the thin 
deposits of shelly matter found on them after twenty -four and forty- 
eight hours, and later. His observations confirm the opinion that the 
shell is formed by the crystallization of the lime in the chitinous sheet, 
and that the form of the lime is not an internal cast of that sheet. Young 
shells of two months average from three-fourths of an inch to an inch in 
longth, and often weigh 3-4 grammes. Stud. Lab. Johns Hopkins Univ. 
ii. No. 4, pp. 427-432, pi. xxxiv. ; abstracts in Ann. N. H. (5) xi. pp. 149 
& 150, and J. R. Micr. Soc. (2) iii. p. 195. 
C. F. W. Krukenberg makes researches into the chemical nature of 
the colouring matter in the shells of Mollusca , and states that the red 
and green pigments in some species of Haliotis , Turbo , and Trochus is 
either biliverdine or nearly allied to it, and that many red, yellow, or 
brown pigments in the shells of Gastropods as well as Bivalves belong to 
the so-called lipochromoids and melanoids. Centralbl. med. ^Viss. 1883, 
No. 44. 
10. Biology . 
H. A. Coutance has experimented upon the resistance of 5 species of 
Mollusca against solutions containing only one or an excess of one of the 
constituents of normal sea-water, chiefly chlorides of magnesia or 
potash and sulphate of magnesia. Each of these is eventually fatal, but 
there is a great difference in the rate of the toxic action of any one solu- 
tion upon the same animal, and a great range in the resistance of different 
Mollusks to the same solution. The salts of soda and magnesia are less 
fatal than those of potash. Venus ( Tupes ) decussata showed a vitality 
far surpassing any other species, and, generally, Bivalves resisted longer 
than Gastropods, Litorina longer than Buccinum. Am. Nat. xvii. p. 1079. 
Pulsations of Helix rufescens 5-6 in a minute just below freezing point; 
it retires for hibernation at a temperature of 38°-40° : F. Ashford, J. of 
Conch, iv. p. 13. 
Some species of snails found in activity in mid- winter ; F. Wiegmann, 
Nachr. mal. Ges. 1883, p. 60. 
Slime-spinning observed in Avion hortensis (Fer.) ; W. Denison Roe- 
buck, J. of Conch, iv. p. 82. In Ancylus lacustris (L.) ; T. D. A. 
Cockerell, l. c. p. 127. 
Achatinella. H. Glanville Barnacle confirms that these snails pro- 
duce musical sounds, somewhat like an ^Eolian harp, by grating their 
shell against wood ; J. of Conch, iv. p. 118. 
A specimen of Unio clasping the under- jaw of Cliehjdra for three days ; 
Todd, Nachr. mal. Ges. 1883, p. 93. 
Boring Bivalves. M. E. Wadsworth suggests that the siliceous grains 
found by Hancock about the foot and mantle of rock-boring Mollusks 
(Ann. N. H. 2, ii.) may be the result and not the cause of the rock exca- 
vation ; Dali, Science, i. p. 422. 
