Xo6 HOURS WITH NATURE. 



leeches as you and I are men. Just try and describe 

 the external appearance of one of them. Very good. 

 I must say you are very clever. You have hit upon 

 the right points : (i) a body made up of a series of 

 equal rings or segments ; (ii) an anterior or head seg- 

 ment, why omit to mention that, behind the head 

 segment is the mouth; (iii) a posterior or anal segment' 

 in which is the anus; (iv) the upper and lower sur- 

 faces of the body, that is, the dorsal and ventral 

 surfaces as they are called in Zoological language. 

 Allow me to supplement your excellent description 

 by stating that if any of these creatures be divided 

 lengthwise through the middle of the body, you get 

 two halves of equal symmetry. 



" There are other details of their structure which we 

 had better postpone the consideration of, until we have 

 made some progress in our study. It would suffice for 

 our present purpose, if I simply call your attention to 

 the fact that there are a great many other animals be- 

 longing to this series. Here, for instance, are some 

 sea-worms from the Andaman reefs ; they are pro. 

 vided with a distinct head, powerful jaws and well- 

 developed locomotive appendages. Do you see those 

 curious-looking objects next to them ? They also are 

 sea-worms ; but as they live a different life, they are 

 differently equipped. Unlike their brethren of the 

 Andaman reefs which lead a free swimming life, these 

 are sedentary in habits, and live in protective tubes or 



