322 FUNCTIONS AND INSTINCTS. 



jP. cornuta, is oviparous in the spring and gem- 

 miparous in the autumn observes, that, in the 

 latter season, it divides itself spontaneously and 

 transversely into two parts above the abdominal 

 orifice, and at the end of ten days each of these 

 parts has acquired the head or the tail that 

 it wanted. He has divided individuals into 

 many transverse pieces and two longitudinal 

 ones, and every piece, in due time, completed 

 itself. It formed eyes, an intestinal tube, and 

 other necessary organs. 



Mr. Dalyell and Dr. Johnson subsequently 

 made similar observations, and by dividing the 

 head had succeeded in producing an animal 

 with two heads; the latter, from the result of 

 several observations, found that each individual, 

 upon an average, might, by spontaneous self- 

 division, produce ten, and this when under 

 constraint ; if at liberty, and in their natural 

 situation, we may conjecture that their reproduc- 

 tive powers might be carried much higher. Dr. 

 Johnson divided one into three equal portions, 

 when the head speedily acquired a new body 

 and tail ; the tail, a new body and head ; and 

 the middle piece a new head and tail. 



From this whole statement it is evident that 

 these pseudo-leeches, to say the least, their sub- 

 stance considered, tend towards the polypes, and 

 possess the same reviviscent powers. In several 

 characters, which I shall notice hereafter, they 



