78 ASHFORD : ON THE DARTS OF BRITISH HELICIDjE. 



in the intervisceral spaces of the mantle cavity — for instance 

 between the branches of the mucous glands or adhering to the 

 exterior of the oviduct or to the albumen gland. Schmidt even 

 found one embedded in the liver. Now there is no communi- 

 cating passage between the interior and exterior of the tubular 

 organs (see fig. i). How then can a dart make its way into 

 such positions. Many authors, looking upon the blades as 

 cutting edges instead of simple strengthening stays, appear to 

 have taken it for granted that in such cases the whole weapon 

 has been actually thrust through the outer integument during 

 conflict. Surely this is mechanically impossible. The dart is 

 too brittle, as Semper remarks, the force exerted is inadequate, 

 and the very form of the dart presents an obstacle to entrance. 

 It rarely penetrates more than one or two millimetres. I 

 would rather suggest that the dart has been first introduced 

 into one of the tubular organs as already described, that it has 

 then lodged in some bend which it could not traverse, and 

 finally, by the constant movements of the animal, has worked 

 its way, point foremost, through the soft, thin wall of the tube. 

 By such means only could it penetrate the liver. Analogous 

 things happen in man. There are scores of cases on medical 

 record of needles, etc., accidently swallowed entire or in frag- 

 ments, making their way through the coats of the alimentary 

 canal and becoming ultimately lodged even in the joints of the 

 limbs. According to Perez the entombed dart is gradually 

 absorbed. 



It is commonly stated that the Helices are provided with 

 darts during the pairing season. This is true but not the whole 

 truth. No doubt more individuals are furnished with them at 

 that period, because it is the time when a great number reach 

 maturity, but darts may be found in situ any month in the year. 

 There is good evidence that a new weapon is formed after the 

 loss of the old one. Individuals possessed of a pair sometimes 

 lose one and retain the other, and some species appear less 

 liable than others to part with their weapon. 



J.C, iv., July, 1883. 



