6 PLANARIA FLEXILIS. 



aperture of the mouth, unlike that of ter- 

 restrial animals, is remote from the head of 

 the planaria. Situated in the belly or un- 

 der surface, nearer to the tail than to the 

 anterior extremity, it receives the necessary 

 aliment to be transmitted to the viscera. 

 Some remarks will afterwards occur on the 

 singular proboscis with which this division 

 of the genus is provided, when treating of 

 those species where its structure has been 

 more easily examined. Towards the an- 

 terior part are two blackish spots on the 

 upper surface of the body, which being 

 subjected to the microscope, are discover- 

 ed to be two groups or clusters of minute 

 jet black specks, of unequal size, and like- 

 wise of unequal number in different ani- 

 mals. In one planaria, each cluster con- 

 sisted of eight specks ; in another, of four- 

 teen or sixteen ; and in a third, which was 

 very small, of eighteen or nineteen, seve- 

 ral being deeper seated in the body than 

 the rest. These specks approach to a glo- 

 bular figure; some are apparently confound- 

 ed together ; and they occasionally appear 



