112 MORPHOLOGY OF INVERTEBRATE TYPES 



lateral blood-vessels with some of the branches and the nervous 

 system in the ventral sinus. Label all organs and corresponding 

 segments using the last pair of nephridia for guide. 



5. Carefully excise with scissors an entire nephridium, put it 

 in a drop of water on a slide and examine under dissecting mi- 

 croscope. Make a drawing about five times natural size and 

 label parts. 



6. Remove a jaw and examine it under microscope in a drop of 

 glycerine. Make a drawing of it about two inches long. 



7. Apply a live leech to the hand or arm. When the skin is 

 pierced remove the leech by putting a drop of alcohol on its 

 head. Wipe off the blood and examine the wound. The three 

 incision lines meeting in the centre correspond to the cutting 

 edges of the jaws. Make a sketch of the wound. 



8. Study the prepared cross-section of a leech under micro- 

 scope. Make a half page drawing of it showing the cuticle, 

 hypodermis, circular, longitudinal, radial and dorso- ventral 

 muscles, the botryoidal tissue, stomach, nephridia, lateral 

 vessels, dorsal sinus, ventral sinus with the nervous system, 

 vasa deferentia (and testes if the section contains them). 



