PHOSPHORESCENCE. 247 



does not proceed from browsing on the plant, but from an 

 exhalation peculiar to the season of reproduction ; and at the 

 same season the Negritse are as foetid as the goat.* Ano- 

 ther species of Helix (H. alliaria) smells at times strongly of 

 garlic. " When fresh taken," says Dr. Turton, " it diffuses 

 an odour exactly like the smell of garlic, so powerful that 

 two or three of them will scent a room for some hours ; "f 

 and, according to Mr. Sheppard, the collector may frequently 

 be guided to its retreat by this exhalation ; J so that what 

 Nature doubtless intended as a beneficial gift, will often 

 prove its bane in these evil days. 



8. PHOSPHORESCENCE. A luminous fluid is secreted by 

 several mollusca. Linnaeus tells us, on the authority of 

 Bartholinus, that, when the Octopus vulgaris is opened in 

 the dark, a light so strong and splendid is emitted, as per- 

 fectly to illuminate the room. The light is, however, 

 faint during life, and not general in the class. The Cleo- 

 dora is the only reputed phosphorescent species among the 

 Pteropods : and as for the Gasteropods, there is also amongst 

 them only one rival of the glow-worm. This is a slug (Phos- 

 phorax noctilucus), a native of the higher mountains in the 

 island of Teneriffe, distinguished by a small pore or disk 

 towards the posterior extremity of the shield, which is of a 

 glossy green in daylight, and luminous at night. || 



Of luminous bivalves there are also few examples. Bosc 

 instances the Solens, or Razor-fish ;^f and Kirby, without 

 weighing his authority, has hence concluded that these are 

 the Dactyles of Pliny;** but he should have known that 



* List.de Coch. Exer. Anat. 146. Of Unio pictorum Lister says, " hi 

 autem musculi, quibus ova nata sunt ad branchias, hircum vehementer ole- 

 bant." Exer. Anat. Tert. 18. 



t Land and Freshwater Shells, 56. 



J Linn. Trans, xiv. 160. The Nanina, also a land-mollusk, secretes a 

 green fluid for defence. " The fluid poured out from the orifice at the base 

 of the caudal horn-like appendage is of a greenish colour ; it exudes when 

 the animal is irritated, and at such times the caudal appendage is directed 

 towards the exciting object in such a manner as to give the animal a 

 threatening aspect." Proc. Zool. Soc. 1834, p. 90. 



Syst. Nat. p. 658 ; edit. dec. Oligerus Jacobseus, quoted by Owen, 

 asserts that the Cephalopods are phosphorescent. Cyclop. Anat. and Phys. 

 i. 526. Mr. C. Darwin noticed that an Octopus which he kept in his cabin, 

 was slightly phosphorescent in the dark. Journal, iii. 7. 



|| " Corpus crassum, latum ; ad partem pallii posteriorem discus margi- 

 natus ex ipso pallio confectus, die viridi lucidus ; nocte phosphorescens." 

 Ann.des Sc. JVaJ.xxviii. 308 ; GRIFFITH'S Cuvier, xxxix. 328. Bosc (Coq. 

 iv. 71), and De Montfort (Conchyl. Syst. ii. 216,) assert the lanthina to be 

 phosphorescent, but neither is good authority on this point. 



H Hist. Nat. de Coq. iii. 9. ** Bridgew. Treat, i. 240, 



