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^ appUed 

 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 



