PAN DE GUAJAIBON 275 



tile designs upon other living things must possess 

 highly specialized methods of defense, Hke our 

 slug, for no skill in hiding or no scheme of pro- 

 tective coloration could wholly save them from 

 the active swarms of carnivorous insects and myrio- 

 pods that range over the grotmd and upon rocks 

 and vegetation. Vast quantities of mollusks, 

 notwithstanding their shelly fortress, fall victims 

 to birds and mice and to other carnivorous mol- 

 lusks, but just why certain species, conspicuous 

 through lack of protective coloration, do not suffer 

 a like fate, is not altogether clear. Upon this 

 particular paredon are two species of mollusks 

 {Eurocopiis hlainiana and Chondropoma sinuata) 

 living more or less in colonies and readily to 

 be seen by reason of their contrasting color with 

 the white limestone. Neither of these appears to 

 be preyed upon by birds, and that they are exempt 

 from attack by other larger enemies is equally 

 certain. The only explanation would seem to be 

 that they are distasteftd as food either on accoi^it 

 of some acrid flavor or poisonous quality. A most 

 striking example of this immunity is furnished by 

 the very beautiful arboreal snails, Polymiia picta 

 of eastern Cuba, which are most conspicuous ob- 



