28 Newton, o» the Helices and Limaces. 



which corresponds in position to this organ in other species, 

 is a tapering tube (fig. 10 d), which by transmitted light 

 presents the appearance of alternate lighter and darker rings. 

 No dart was to be found in this tube in any of the specimens 

 examined. Schmidt (' Zeitsch. f. Malakozoologie/ 1850, p. 1, 

 and 1852, p. 1) considers the dart to l)e very important as a 

 means of determining the relations of the species of Helix ; 

 and gives tables of those which possess two darts, of those 

 with one dart only, and of those which are devoid of any 

 dart. The only anatomical difference between H. nemoralis 

 and H. hortensis appears to be in the form of the dart. 



The flagellum, which in H. aspersa and H. pomatia is very 

 long (PI. V, fig. 7fl), gradually shortens in //. nemoralis and 

 H. hortensis (fig. 8//), H. rufescens (fig. 9fl), H. cantiana (fig. 

 10^;^), and H. virgata (fig. 11 fl) and, as has been mentioned, is 

 altogether absent from the Limaces.; L. ayrestis, however, 

 having the trifurcate gland in its place (fig. 4 fl) . 



The multifid vesicles present some variations in the dif- 

 ferent genera and species ; H. pomatia and H. aspersa have 

 them large and foliated (fig. 1 g), communicating by two ducts 

 with the vagina ; in H. nemoralis and H. hortensis (fig. 8 g) 

 there are only two or three long csecal tubes upon each side, 

 which terminate, as before, by two ducts ; these tubes vary in 

 length in different individuals. In H. rufescens there are 

 eight tubes, which open into the vagina by four ducts (fig. 

 9^). In H. virgata they are irregular in form, and not 

 laterally symmetrical (fig. 11^). 



Limax differs from Helix in the arrangement and number 

 of its muscles. There are in the Helices two muscles, which 

 have their origin, together with the retractors of the foot, 

 buccal body, and tentacles, upon the columella of the shell, 

 and are inserted into the parietes of the head immediately 

 within the inferior tentacles. This pair of muscles was not 

 found in the Limaces. The series of muscles which retract 

 the foot in Helix are not present in Limax. The retractor 

 muscle of the penis (when present) is attached in Helix to- 

 the floor of the pulmonary chamber, and midway between 

 the extremities of the penis (figs. 7, 8, 9, and 11 rj)), whilst 

 in L. maximus and L. flavus it is attached to the extremity 

 of the penis (fig. Irp), and behind the pulmonary chamber, 

 somewhat towards the left side. In the L. Sowerhii and 

 L. agre&tis its attachment to the penis is the same as in the 

 Helix (fig. 2rp and fig. 4 rp). H. cantiana and Arion ater 

 do not appear to possess this retractor of the penis. L. 

 Sowerhii has an additional annular band of muscular fibres 

 (fig. 2 rp'), which is attached to the penis at some little dis- 



