ASHFORD : OX THE DARTS OF BRITISH HELICID^. 1 65 



The blades of the dart are more or less transparent. They 

 originate rather high up above the basal expansion (fig. 4), 

 increase gradually in prominence to about the middle of their 

 extent, where they attain a maximum breadth, and diminish 

 upwards about as gradually, disappearing a short distance from 

 the sharp solid point of the weapon. Their outer margins are 

 invariably sharp — never channelled. The difference in the 

 amount of prominence of the two pair of blades, exceptionally 

 observable in some other species, appears- to be a tolerably 

 constant characteristic of the dart of ^ 7iemoralis. Bet«-een two 

 consecutive blades the shaft is rarely quite smooth, the inter- 

 vening space being usually interrupted by crescentic films, 

 extending transversely from one blade to the next, variable in 

 number and distance ; they are moderately transparent, slightly 

 iridescent in certain lights, and generally disappear by short 

 exposure to a heated solution of caustic potash. They may be, 

 as Schmidt suggests, disrupted portions of an investing mem- 

 brane, and the ragged condition they sometimes present favours 

 this view, but if so, why do they often assume a crescent-form ? 

 Among British Helices these curious septa occur only in the 

 present species and in H. aspersa, and are chiefly confined to the 

 more matured darts. 



There may sometimes be noticed in this dart a verv slight 

 curvature of the shaft more particularly in the apical half. It 

 is rather difficult to determine when this is natural and when 

 accidental. Every one who has cut out the dart of H. nejuoralis 

 with the dissecting knife must have observed a limited amount 

 of plasticity in the organ ; on this account its ultimate straight- 

 ness or curvature, when dried by exposure, may depend upon 

 the way in which it is laid out by the manipulator. But allow- 

 ing that the dart of this species is not invariably quite straight, 

 there appear to be no grounds whatever for the statements of 

 Sheppard and Neumann that a relation subsists between the 

 condition of the dart in this respect and the distribution of 

 bands upon the shell (cf. Gray's Turton's Manual, 1840, p. 134). 



