184 Scientific IntcUig-ence. — Zoology. 



ments it appears, that, if an incision be made longitudinally in- 

 to the head of the animal, so as to separate its eyes from each 

 other, if the cut has not been carried very far down, it will heal 

 in the ordinary manner ; but, if the head be absolutely cleft in 

 twain, then, according to the extent of the fissure, there will be 

 a mass of new matter formed by each half of the head, which 

 will either join the two halves together, forming a head of ex- 

 traordinary size, and bearing in it one or two additional eyes ; 

 or each old half, thus cleft, will form the new matter into ano- 

 ther half, with an eye ; and so the animals have two complete 

 and entire heads. If the fissure be carried farther down through 

 the body of the animal, then not only will there be two heads 

 but two bodies also formed, joined together only by the tail ; 

 and when this is the case, so little unanimity exists between 

 these Siamoid twin-plauaria?, that they never pull or swim the 

 same way; and so violent are their efforts, that they frequently, 

 in the course of two or three days, tear the only remaining bond 

 or union, tlieir tail, in sunder, and then two distinct and perfect 

 animals result. If, in common planariae, the head be cut en- 

 tirely £)fF, a new head will be formed ; and, if their lower extre- 

 mity be removed, it will produce a new tail. In a planaria, 

 which, by the operation above described, had been invested with 

 two heads, these *' nova capita" were successively severed for 

 three several generations, and were immediately and perfectly 

 renewed, and subsequently the animal was cut through just be- 

 low the artificial bifurcation, and then only a single head was 

 produced ; so that 4n this more than simple " capital'- operation, 

 a single headed animal became a biceps, and, after having the 

 «se of six heads in succession, was subsequently reduced to the 

 possession of a single one. When one of these animals is cut in 

 half, the head or anterior extremity swims away as if nothing 

 bad happened, and speedily retails itself ; but the tail swims to 

 -the bottom, and remains torpid for two or three days, by which 

 time it has formed for itself a head. If a planaria be cut i»to 

 three pieces, the head will form a new body and tail, the tail a 

 new body and head, and the middle section or body will pro- 

 duce both head and tail. If a quarter be removed by making 

 a longitudinal section through the head, and half down the 



