244 URINARY SECRETIONS. 



to alcohol, like cochineal and the succus of the animal of 

 Turbo (Scalaria) clathrus ; but it communicates its very dis- 

 agreeable odour to it most copiously, so that opening the 

 bottle has been more powerful in its effects on the olfactory 

 nerves than the effluvia of assafcetida, to which it may be 

 compared. All the markings which had been alkalised and 

 acidulated, together with those to which nothing had been 

 applied, became, after washing in soap and water, of a uni- 

 form colour, rather brighter than before, and were fixed at a 

 fine unchangeable crimson."* 



The fluid excreted by some of these mollusks is of a green 

 colour. When the snail of the Purpura patula is retracted 

 within its shell, if you press on the operculum, a very consi- 

 derable quantity of a greenish liquor is shed, but it becomes 

 a deep purple in drying ; and Adanson is a good authority 

 for saying that the greater number of the species discharge 

 a similar tincture.-)- The colour , of it appears, however, to 

 be more permanent in the species of Cerithium, a genus not 

 much removed in nature from Purpura. Two specimens of 

 Cerithium armatum were brought alive to London from the 

 Mauritius, kept, during their long voyage, not in sea-water, 

 as you might imagine, seeing that the animal is aquatic, but 

 in a dry state, and affording a remarkable illustration of the 

 tenaciousness of its life. The animal was apparently healthy 

 and beautifully coloured : it emitted a considerable quantity 

 of bright green fluid, which stained paper of a grass-green 

 colour; it also coloured two or three ounces of pure water. 

 This green solution, after standing for twelve hours in a 

 stoppered bottle, became purplish at the upper part; but 

 the paper retained its green colour though exposed to the 

 atmosphere. J A tincture made by immersing the animal of 

 Cerithium telescopium in spirits, became of a dark verdigris 

 colour, which it retained for some weeks. 



6. URINARY SECRETIONS. Blainville seems to be of 

 opinion that the coloured secretions now noticed are analo- 

 gous to the urinary secretion of vertebrated animals ; 1 1 but 

 although the opinion has been adopted by many authors,^ 

 yet of its correctness doubts may be reasonably entertained. 

 Besides their purple fluid, the Aplysiae occasionally dis- 

 charge, but in small quantities, a whitish acrid one, secreted 

 by a gland composed of little round hyaline grains, and 



* Test. Brit. Supp. 106. t Senegal, Coquil. i. 106. 



J Proc. Zool. Soc. iii. part ii. 22. Lib. cit. iii. part ii. 22. 



|| Manuel, p. 160. 



IT Raspail's Organic Chemistry, p. 529 ; Tiedemann's Comp. Physiology, 

 p. 220. 



