1898.] NATUEAL SCIENCES OF PHILADELPHIA. 243 



plied by keeping slugs in captivity. Does regeneration of the lost 

 member take place, and if so, is the renewed tail structurally like 

 the amputated one, or does loss of the tail result eventually in 

 death ? What animals persecute Prophysaon f Observations upon 

 these questions might go a long way toward explaining the present 

 utility of tail amputation, though they may not indicate the mode 

 of its origin. Without knowledge of the final consquences of am- 

 putation to the slug, or what its natural enemies are, speculation 

 upon tail excision is idle. In an analogous case now well known, 

 that of Helicarion in the Philippine Islands, Semper 15 states that 

 every species he examined " possessed the singular property, which 

 many lizards have — particularly the Geckos — of shedding their tail 

 when they are seized somewhat roughly at a little way behind the 

 shell. This they do by whisking the tail up and down with extra- 

 ordinary rapidity, almost convulsively, till it drops off; if the creat- 

 ure is held by the tail, it immediately falls to the ground, where it 

 easily hides among the leaves. If it is laid flat on the hand, the 

 rapid wagging movement is strong enough to raise the body with a 

 spring into the air, so that it falls over on to the ground. These 

 snails at first constantly escaped me and my collectors in this way, 

 and not unfrequently we had nothing but the tail left in our hands. 

 According to Guilding's observations the same peculiarity of part- 

 ing with the hinder prolongation of the foot characterizes the West 

 Indian snail Stenopus. I ascertained by further investigation that 

 in a free state of nature such self-mutilation not unfrequently occurs, 

 for about a hundred specimens of Helicarion gutta, which is ex- 

 tremely common in the north-east of Luzon, I found, perhaps, ten in- 

 dividuals that had shed their tails, or, to speak more accurately, the 

 hinder end of the foot, and had the stumps partly healed, or the foot 

 to some extent grown again. Now, this hinder portion of the foot 

 is the most conspicuous part of the snail's body, and it may be sup- 

 posed that it is, in most cases, the part first seized by the reptiles or 

 birds that prey upon them ; but, startled by the escape of the body, 

 they would soon learn to recognize, by the form of the tail, those 

 species which were capable, by this self-amputation, of depriving 

 them of the larger and probably the only valuable portion of the 

 prey. In this way the species of the genus Helicarion can escape 

 the pursuit of their enemies better than they otherwise could on 

 account of their exposed mode of life." 



15 Animal Life, Chapter XII. 



