REPRODUCTION OF DESTROYED ORGANS. 133 



chitinons cuticle. There exists, nearly alwa3's, a bj^ssal gland 

 at the base of the foot. 



REPRODUCTION OF DESTROYED ORGANS. 



It appears from the experiments of Spallanzani, that snails, 

 whose ocular tentacles have been destroyed, reproduce them 

 completely in a few weeks ; others have repeated the trial with 

 a like result. But there is some doubt whether the renewal 

 takes place if the brain of the animal be removed as well as its 

 horns. Madame Power has made similar observations upon 

 various marine snails, and has found that portions of the foot, 

 mantle, and tentacles, were renewed. Mr. Hancock states that the 

 species of Eolis are apt to make a meal otf each other's papillae, 

 and that, if confined in stale water, they become sickly and lose 

 those organs ; in both cases they are quickly renewed under 

 favorable circumstances. 



The Cephalopoda frequently lose a portion of an arm or the 

 entire limb in the course of their active existence, but soon develop 

 another from the stump of the destro^-ed member, and only 

 differing from it in being less colored. 



In some cases mollusks can spontaneously detach portions of 

 their body. I have already shown in the chapter on sexual 

 organs how the hectocotylized arm of the Octopus becomes 

 detached from its owner and remains within the pouch of the 

 female, and that a similar specialized arm developes in du.e time 

 to take the place of the lost member; only to detach itself in 

 turn. Quoy and Gaimard several times saw the Harpa ventricosa 

 amputate the posterior portion of the foot by muscular contrac- 

 tions, the lost part being subsequently replaced by growth. In 

 two Cuban Helices also {H. C7'assilabris and H. imperator), Dr. 

 Gundlach has seen a similar amputation and somewhat rapid 

 regeneration. 



The bivalve genera Solen and Solecurtus readily lose a portion 

 of their siphons. Fischer has often found the detached extremities 

 of siphons alongside the beds of Solen marginatus in the Basins 

 of Arcachon. 



I have already considered the renewal of fractured portions of 

 the shell (pp. 20, 32) and operculum (p. 49), as well as the 

 abnormal duplication of both (p. 52). 



