Giard, C. R. Soc. Biol. v. 1893, p. 473.
See M‘Intosh, Ann. Mag. Nat. Hist. (ser. 4) ii. 1868, p. 276.
Lankester has suggested that a strong acid is secreted for the purpose, see Ann. Mag. Nat. Hist. (ser. 4) i. 1868, p. 233.
M‘Intosh, Ann. Mag. Nat. Hist. (ser. 6) xiii. 1894, p. 1.
Dalyell, The Powers of the Creator revealed, ii. 1853, p. 217.