ASHFORD : ON THE DARTS OF BRITISH HELICID^. 20I 



" Perhaps we may be told hereafter," he adds playfully, " that 

 this excretory fluid" (connecting the dart and tubercle) "is 

 used as a cord to regain these darts after they have been dis- 

 charged." 



Immature darts in various stages are to be met with rather 

 frequently (say one in seven). It will be sufficient to refer to 

 fig. 17 where three examples are represented to the same scale. 

 The blades of a have made some advance, in b they are just 

 sprouting, and the section of c would probably be quadrangular. 

 The lower part of a dart approaching completion is shown 

 much enlarged in fig. 16. This presents some interesting 

 features. Observe the formative process going on in the lower 

 part of the blades, the portion not included in the figure being 

 finished. The base of the shaft is just beginning to enlarge, 

 and it is evident the conical expansion when formed will add 

 its own length to the present length of the dart. For if this 

 conical portion were produced by the addition of material to 

 the exterior of the curved surface already existing, the final 

 basal marginal ring would necessarily be very thick, whereas in 

 the completed dart we always find that margin extremely thin. 

 It does not necessarily follow, but it seems probable that the 

 annulus of little rods (see fig. 13) cannot be formed, or at least 

 cannot make attachment to the dart until this increment has 

 been added. The blades meantime are embedded in the sides 

 of the inner sac, in deep trenches, very conspicuous in the 

 case of H. aspersa, and first described by Cuvier. 



Free darts, as foreign bodies, occur rather frequently in the 

 species under notice. One such I found between the sperma- 

 theca and oviduct, another among the branches of the mucous 

 glands, the dart-sac in this case containing its proper weapon, 

 a third in the common genital passage, point downwards, a 

 fourth in the integument beneath the mantle. On the 9th of 

 April, about seven days after the general exodus from hiberna- 

 tion, one individual having a dart complete with annulus in its 

 sac, harboured in its other organs two errant darts, one with its 



