228 HUGH WATSON. 



pacta Cox & Hedley and P. atramentaria {Shuttl.) these 

 papillae are glandular in structure. Now in Peripatus, an 

 arthropod genus whose habits are not unlike those of the 

 carnivorous snails and slugs, there are two large slime-glands 

 which open on the oral papillas, and their secretion is used to 

 entangle the prey. The carnivorous slug A top us also 

 possesses two large glands opening oue at each side of the 

 mouth; and Simroth/ who first discovered them, has suggested 

 that their function may be similar to that of the slime-glands 

 of Peripatus. We have already seen that the pedal gland 

 is developed to an unusual extent among the carnivorous 

 genera. Now this gland also opens close to the mouth, and I 

 would suggest that its secretion may play some part in over- 

 powering the prey. The form of the pedal gland in Apera 

 has come to resemble in some respects that of Simroth^s 

 glands in Atopus, and nearly twent}^ years ago Andre ^ 

 suggested that the secretion of the pedal gland in the 

 Sty lommatophora might be used in feeding as well as in 

 locomotion. We may at least say this : that the remarkable 

 development of the pedal gland in the Agnatha, as well as 

 the presence of the labial feelers, may not improbably be due 

 to their predaceous habits. 



It is unnecessary to attempt to prove that the acquisition 

 of carnivorous habits might lead to a modification of the 

 radula and the surrounding structures: obviously these would 

 be among the first organs to be aifected. It will be sufficient, 

 therefore, if I point out the chief ways in which the radula 

 has become transformed. In the first place, it has inci-eased 

 in size, and especially in length, and become capable of far 

 greater- protrusion than in the herbivorous forms. Secondly, 

 the individual teeth have become much larger, especially 

 those occupying an analogous position in the radula to that 

 held by the canine teeth in the jaw of the Mammalia; and to 

 make room for these, the central teeth and those at the 

 extreme edges of the radula have become vestigial or have 



' ' Naturwiss. Woelieiischr..' 1901, vol. xvii, p. 122. 

 ^ • Revue Suisse cle Zoologie." vol. ii, p. 332. 



