1 66 ASHFORD : ON THE DARTS OF BRITISH HELICID^. 



Many years ago Adolf Schmidt undertook a careful examination 

 of series variously biinded, with this subject specially in view, 

 and found nothing to corroborate the statement referred to ; 

 indeed he scarcely admits that the dart of H. nemoralis, in a 

 natural state, is ever otherwise than straight. 



Fig. 6 represents the condition of an immature dart when 

 about 3 mm. long. The base is cylindrical, the central part of 

 the shaft simply angulated, the annulus not formed. At a later 

 stage the four nascent blades make their appearance with their 

 jagged edges and unsymmetrical outline. I have now before 

 me a dart nearly 6 mm. long. The blades are nearly complete, 

 but the short narrow base still shows no indication of the 

 trumpet-shape . termination (fig. 5) characteristic of the mature 

 weapon. That enlargement therefore, as well as the annulus, 

 must be acquired during the last two millimetres of growth, in 

 some instances at least. 



I once met with what may be called a case of hernia of the 

 sac, the dark inner sheath having burst through the end of the 

 outer coat so as to protrude about 2 mm. The sac contained 

 a dart about 7 mm. long, into the conical base of which the 

 annulus had been forcibly driven so as to be nearly concealed 

 from view. 



Including only such as had fully-formed shells, I fiind that 

 of the individuals examined between March and September 69 

 per cent, had darts, 21 per cent, had not formed their darts, and 

 10 per cent, appeared to have lost them. 



I am indebted to Mr. J. W. Taylor for living examples from 

 Scarborough. The figures are drawn from specimens obtained 

 near Christchurch. 



8. Helix hortensis Miiller, pi. vii., figs. 7 — it. Dart-sac 

 small, subclavate ; leaden blue when mature. Dart 

 curved, moderately expanded at the base ; furnished 

 with four channel-edged blades ; annulus of 14 to 16 

 rods. Length 4 mm. 



Except in size the dart-sac of H. hortensis is much like that 



oi H. ne7?ioralis, and the remarks on the colour of the latter 



J.C, iv., April, 1S84. 



