18 PLANAKIA FLEXILIS. 



indigestible, might escape before its natu- 

 ral dispersion among the vessels. The 

 three planariae at length literally seemed 

 burst from their excessive voracity ; and a 

 portion of the tail of one was tore away in 

 its struggles. Notwithstanding every pre- 

 caution for their preservation, all perished 

 within two or three days ; and putrefaction 

 rapidly dissolved their lacerated bodies. 



Some animals, especially those whose 

 success is uncertain in capturing prey, can 

 survive wonderfully long entirely devoid of 

 aliment. But when the opportunity comes, 

 their voracity is proportioned to the absti- 

 nence endured. Adhering to the same 

 spot, the polypus and sea anemone can on- 

 ly extend their retractile tentacula to 

 seize whatever victim may occasionally 

 stray within their compass. A wide mouth 

 expands beyond the diameter of the base 

 to receive it ; the capacity of the body is 

 dilated infinitely above its ordinary di- 

 mensions, which are again reduced as the 

 food is consumed by digestion. No ani- 



