146 EXPLANATION OF THE FIGURES. 



10. APlanaria 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. 



17. Planaria Velox, of the natural size, and 



magnified. 



18. Planaria Edinensis, magnified. 



