202 ASHFORD : ON THE DARTS OF BRITISH HELICIDiE. 



point penetrating the ovotestis, the other in two fragments, of 

 which the basal portion with annulus attached, was partly 

 embedded in the inferior margin of the albumen gland, the rest 

 minus the point adhered to the exterior of the oviduct. From 

 their discoloured and partly disintegrated condition these frag- 

 ments had probably been the animal's guests throughout the 

 winter. 



By direct observation of this species M. Perez satisfied 

 himself that anew dart is formed to supply the place of a lost 

 one. Selecting coupled individuals he kept them in captivity 

 and dissected some after an interval of twenty-four hours, others 

 after two days, and so on. He says that sacs opened after a 

 lapse of one day already contained fine calcareous needles 

 usually I '5 to 175 mm. long; those examined after two days 

 had darts about 3*5 mm. long; on the third day they were 

 6 to 7 mm. ; and on the fifth or sixth day renewal was complete. 



Summing up as before (shells perfect always understood), 

 I find 56 per cent, had darts — one third of them more or less 

 immature — 25 per cent, had not formed darts, and 19 per cent, 

 had mature but empty sacs. 



Darts may be found present in H. aspersa in every month 

 of the year. In the middle of December, eight full-grown shells 

 were selected from a hibernating group ; six of them yielded 

 darts. As no satisfactory evidence is yet forthcoming that the 

 formative process goes on during winter sleep, we must conclude 

 provisionally the six individuals referred to had either retained 

 the darts used during the preceding summer, or having lost their 

 weapons had renewed them in late autumn before retiring for the 

 winter. 



All the figures are from examples collected at Christchurch. 



J.C, iv., July, 1SS4 



