PLANARIA FELINA. 59 



ing to institute a series of experiments, for 

 the purpose of ascertaining the relative 

 progress of regeneration, during a variety 

 in the permanence of temperature. Is 

 every kind of vegetation, both in plants and 

 animals, accomplished by the same quan- 

 tum of heat, though unequally distributed 

 with respect to time? Will 800 applied 

 in ten days, at the rate of 80 daily, have 

 the like effect in renewing the defective 

 organs of a planaria, as 800 continued for 

 twenty days, at the rate of 40 ? Two 

 points would necessarily be kept in view ; 

 first, the degree of cold when vegetation 

 cannot advance ; secondly, the degree of 

 heat injurious to the species. It appears 

 to me, that planariae soon begin to suffer. 

 One which had been exposed to the heat 

 of 99 survived; but higher degrees seem 

 fatal. The success of the experiment 

 would thus depend on chusing a proper 

 medium. 



If this be the sole and natural mode of 

 propagation among planarise, it presents a 



