13: Read over the introduction to the phylum, pp. 193-194.

13A: Study external features of the clamworm, highlighting the terms listed above. Be prepared to identify other worms as polychaetes. How would the movement of a clamworm differ from that of an earthworm? We will have clamworms to dissect, but before doing so, dissect the earthworm first to appreciate the overall annelid internal body plan. Once you do that, dissect the clamworm in a similar way. How does bearing parapodia and a developed head alter the internal appearance of the clamworm compared to the earthworm? Follow up your dissection with a cross-section slide. Can you interpret the structures in the slide?

13B: Examine the behavior of the live earthworms. Why do the earthworms prefer a damp surface? Please dampen the paper towel with the supplied nonchlorinated water--it's less irritating to the worms. Examine major external and internal features of a preserved earthworm, highlighting the terms listed above. Also, follow up on the internal anatomy by examining a cross section slide of an earthworm. Be prepared to define metamerism and how your examination of the earthworm highlights its metameric nature. In particular, be prepared to describe the modifications of the eucoelom (true body cavity) of an earthworm.

13C: Examine external features of a preserved leech, highlighting the terms listed above. How are leeches similar to earthworms? How are they different? Whole mount slides of leeches may offer additional details. Dissect open a preserved leech after dissecting the earthworm. How does its internal structure compare/contrast to that of the earthworm. What might this mean in terms of movement, for example?