146 EXPLANATION OF THE FIGURES. 



10. A Planaria Felina with two heads, the 

 second of which has been artificially produced ; 

 seen from below. 



11. 12. The upper and under surface of the 

 Planaria Arethusa. 



13. The upper surface of another of these 

 animals, somewhat magnified, to shew the posi- 

 tion of the eyes. The clear line indicates the 

 site of the proboscis ; the lower extremity being 

 its aperture on the other side. 



14. A complete animal, reproduced from a 

 fragment such as 9. which separated from the tail 

 of 11. 12. 



15. The Planaria Nigra, magnified, to shew 

 the site and operation of the proboscis. c, its 

 mouth ; , the head of the animal ; b, its tail. 

 The Planaria is somewhat more contracted when 

 this organ is so much extended as represented 

 here. 



16. Planaria Graminea of the natural size, 

 and as seen by a magnifier. 



1 7. Planaria Velox, of the natural size, and 

 magnified. 



18. Planaria Edinensis, magnified. 



