102 DIGESTIVE ORGANS. 



this enlarged space is furnished witli a number of folds which 

 may be regarded as substitutes. 



In Conus there is only a single gland (xv, 80), and it is very 

 doubtful whether this is salivary in function ; Troschel considers 

 it a poison-gland. 



In addition to the salivary glands there is found in Murex (not 

 observed in other genera), a gland lying above the oesophagus ; 

 it is thick, granular in structure, of liver-brown color, divided 

 into several large lobes and opens into the oesophagus by two 

 ducts. Its purpose is unknown. In Dolium, the glands are 

 enormous, each consisting of two enlarged portions, the anterior 

 one compact and secreting the saliva, the posterior much larger, 

 membranous, and the secretion of which is distinctly acid, a 

 property first detected by Troschel, and afterwards observed in 

 this and in several other mollusks by a number of investigators.* 

 Troschel states that if the Doliuvi galea is irritated, it will 

 protract its proboscis as much as a foot, and eject from it a 

 quantity of clear fluid, with a very acid smell, and producing effer- 

 vescence upon calcareous soil. The liquid has been ascertained 

 to contain several per cent, of free sulphuric acid, and about 4 

 per cent, of hydrochloric acid.j- How the mollusk secretes this 

 acid, and how it protects its own tissues and the epithelial cells 

 of the glands themselves against its action is not at all understood. 

 The acid secretion does not appear to be taken into the stomach, 

 for Troschel found in the stomach of Dolium seaweed and calca- 

 reous remains, which, when artificially brought into contact with 

 the acid, immediately commenced to dissolve. He thinks the 

 secretion is for defensive purposes, and it has been suggested by 

 others that it assists carnivorous mollusks like the Murex in 

 boring into the shells of their victims — usually bivalve mollusca. 



The liver is a brownish or greenish gland of extraordinary size, 

 which forms almost the whole of the usually spirally coiled hinder 

 portion of the animal from the stomach back, giving up to the 

 sex-glands but a small space. The form of the liver is, therefore, 

 very much the same as that of the posterior portion of the body 

 itself. It is lobulate, and when removed to water is found to be 

 acinose. The acini at their ends are cleft into many digitiform 

 processes ; the ducts from the acini unite, then those of the lobes, 

 with frequently sirius-like dilatations, but ending as two bile ducts, 

 placed one before the other, and which correspond to the largest 

 subdivisions of the liver, and approach and, finally, enter the 



* Researches upon the organs which, in the gasteropods, secrete sulphuric 

 acid. By Prof. Paolo Panceri, Jour, de Conch., 3d ser., ix, 308, 1869. 



f De Luca and Panceri have ascertained tlie existence of free sulphuric 

 acid in the salivary product of Murex trunculus and M. brandaris. Ann. 

 8c. Nat., 87, 1867. 



