108 PLANARIA ARETHUSA. 



feeding readily when supplied with the wa- 

 ter on the south of the town, they lan- 

 guished and died when transferred to the 

 opposite quarter. There the water com- 

 monly used by the inhabitants proved insa- 

 lubrious. The naturalist should therefore 

 always search for what is already inhabited 

 by animated beings visible to the naked 

 eye, before consigning those to it in whose 

 preservation he is interested. 



The subsequent alteration of proportion 

 in the different parts of a fragment sepa- 

 rating in the species arethusa, is not dissi- 

 milar from what is witnessed in the pro- 

 gress of the felina. Between the eleventh 

 and seventeenth of January, a portion de- 

 tached itself from the extremity of another 

 of the six animals selected for observation. 

 On the tenth of February, its figure and 

 proportions approached to those of a plana- 

 ria in miniature ; the original breadth was 

 greatly diminished ; the head, instead of 

 being a shapeless projection, was connected 

 to the body by a well-formed neck; and the 



