CHAPTER XV 



PHYLUM ANNELIDA (Segmented Worms) 



Laboratory Exercises 



258. The Earthworm (Helodrilus or Lumbricus). — The prin- 

 cipal work should be done with living worms. For whatever 

 anatomical work is undertaken, specimens may be killed by 

 exposure to fumes of chloroform while wrapped in cloth moist- 

 ened with water; they should then be pinned out straight, and 

 hardened in an abundance of alcohol. If needed in the winter 

 they may often be found under manure heaps, or about green- 

 houses. They may be kept alive in flower pots containing 

 moist earth. 



1. Promorphology; General Form. — Is there an anterior and 

 a posterior end ? How distinguished ? Is there any distinction 

 of dorsal and ventral surfaces ? If so, what ? Is there bilat- 

 eral symmetry? What external evidences of segmentation do 

 you find? How are the similar units {metameres or segments) 

 arranged ? Compare with the condition in the starfish. Com- 

 pare the metameres of different parts of the body, noting differ- 

 ences. Is the body divisible into regions {i.e., groups of similar 

 metameres) ? Locate (by numbering the segments) all such 

 regions. How many segments in the animal ? To what extent 

 does this vary in different specimens? Show by a series of 

 diagrams the shape of the animal, and the shape and size of 

 cross sections in various regions. 



2 . Activities. — Describe, after careful observation, the method 

 of locomotion in the earthworm. Place the worm on a 

 rough board; on a plate of glass. What is the difference ? And 

 why ? Compare the various parts of the body as to size, during 

 movement. Cause of the difference ? Can each end move fore- 

 most? What seems to determine which end shall protrude as 

 the result of the muscular contractions ? 



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