PLANARIA NIGRA. SI 



period seldom coincide. By the most re- 

 cent, four were detected in the very act of 

 issuing from the egg, on the eleventh of 

 April, twenty-five days after it was laid : 

 all lively, the marginal specks very distinct, 

 but not of equal number. An egg of the 

 same species was at the same time hatch- 

 ed in twenty-one days : but a fortnight 

 later, a third of the like age was still entire. 

 Therefore, the period required for exclu- 

 sion, is to be calculated at twenty-one days-, 

 or longer ; and it is certainly affected by 

 the temperature of the atmosphere. The 

 oviduct and relative organs appropriated for 

 perpetuation of the species, are most like- 

 ly situated in the second ventral pore : 

 neither this nor the first is conspicuous in 

 all planariae ; in many they are scarcely 

 perceptible, and appear connected in some 

 by a lighter line on the abdomen. 



But, independent of propagating by eggs, 

 the black planaria, from that indestructibi- 

 lity of life preserving it under mutilation, 

 is privileged to multiply its species in pro- 

 1 



