LABORATORY WORK: EARTHWORM. 



The student should be supplied with a live earthworm, 

 and also with a specimen killed by placing in a dish in 

 which is a bit of cloth dampened with chloroform, the 

 whole being covered so as to prevent escape of the fumes. 

 After death the worm should be pinned out straight, and 

 hardened in plenty of alcohol. 



Is the body cylindrical throughout? Is it bilaterally 

 symmetrical ? Can you distinguish between dorsal and 

 ventral surfaces ? Is the body apparently made up of seg- 

 ments ? Are they all essentially alike ? Draw the worm 

 through the fingers; does it move with equal ease in both 

 directions ? Examine the head end for the mouth ; is it dorsal 

 or ventral in position ? Is the ring (preoral lobe) in front 

 of the mouth complete ? How is it attached to the next 

 ring ? Examine the surface of the body with a lens for 

 bristles (setae). Do you find them on each segment ? How 

 are they arranged on the segment ? Where is the vent ? 

 About one fourth the length of the body from the anterior 

 end notice that certain rings are enlarged and swollen, and 

 that the lines between the segments tend to be obliterated. 

 This is the clitellum. How many segments are included 

 in it ? The clitellum is a glandular structure to secrete 

 the cases or cocoons in which the eggs are laid. 



Hold a living worm near the anterior end. Does it pro- 

 ject a proboscis from the mouth ? Look on the back and 

 see the red dorsal blood-vessel showing through the skin. 



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