THE EARTHWORM 

 Phylum Annelida Class OLiGOCHiETA 



I. BEHAVIOR AND EXTERNAL FEATURES 

 Exercise 1. — General Activities. 



(a) The following directions apply to any of the species of Lum- 

 bricus. Place a vigorous, active worm upon wet filter paper in a 

 dissecting pan and carefully observe the mode of locomotion. How 

 does it elongate and contract? Is there a rhythm in these changes? 

 Can you see the minute, stiff spines that project through the body 

 wall? Can they be drawn in? Draw the worm through the fingers 

 and feel the spines, or setae. How many are there on each ring, or 

 somite? Place the worm on its back. Does it right itself? Will it 

 crawl backwards? Compare the anterior and posterior ends, the 

 dorsal and ventral surfaces, the right and left sides. Which are alike? 

 Touch various parts of the worm to find out which are the more sensi- 

 tive. Note the movements of the soft lobe, the prostomium, above the 

 mouth. On the mid-dorsal line look for the dorsal blood vessel which 

 shows through the body wall. Does it pulsate? Which way does the 

 blood move? 



Exercise 2. — External Features. 



(b) For this study a preserved worm will be used. Is the number 

 of somites the same in all specimens? On the ventral surface may be 

 seen light-colored swollen areas, the skin glands. Notice the smooth 

 swollen band, the clitellum, which passes around the animal. What 

 somites are occupied by the clitellum? By means of the handlens, 

 examine the seta in different regions. Locate the anus. Look on the 

 fourteenth somite, near the ventral setae, for the minute openings of the 

 oviducts, or ducts for the discharge of eggs. On the fifteenth somite, 

 swellings mark out transverse slits on each side, the openings of the 

 ductus deferentes (vasa deferentia), or ducts for the discharge of 

 sperm. Make a figure (X 2), showing the anterior end as far back 

 as a point just behind the clitellum, from ventral view. Number the 

 somites and locate accurately all the structures observed. Make a 

 similar figure of the posterior ten somites. 



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