CHAPTER VI 

 BRANCH ANNULATA: THE TRUE WORMS 



THE EARTHWORM 



For the purposes of this study both living and dead 

 earthworms should be provided. The larger the specimens, 

 the more satisfactory will be the results. Kill some of the 

 worms by enclosing them in a covered dish containing a 

 little ether or chloroform. If the internal anatomy is to 

 be studied in such freshly killed specimens, they should be 

 dissected under water in a shallow dish having the bottom 

 covered with wax or sheet cork. The internal anatomy 

 may also be studied in specimens hardened in alcohol, 

 although some of the more delicate parts are likely not to 

 show so well as they do in fresh specimens. 



MOVEMENTS AND EXTERNAL ANATOMY 



I. — Place a living earthworm on a sheet of paper. 



Watch its movements. Determine which is the anterior 

 end and which the ventral surface. Is it able to move 

 backwards .■■ By what means does it move .■■ Is there 

 a decrease in diameter when the worm stretches out ? 



II. — Find the bristle-like setae on the ventral surface. 

 How many rows of them are there.' Toward which 

 end of the body do the tips of the setae point ? 



III. — Notice how the earthworm is divided into narrow 

 rings, or segments, throughout its length. Study the 

 first segment ; the lip-like projection above the mouth 

 is called the prostomium. 



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