Questions.
- What is the extent of the body cavity, anteriorly and posteriorly? What is its shape?
- What, in general, is the shape of the food canal? How many external openings has it?
- Into what regions is the food canal differentiated? Suggest one advantage of having these specialized regions.
- How is the alimentary canal of the worm kept away from the body walls? Why have it thus supported?
- What is a septum? How many septa are there? What vessels and tubes pass through a septum?
- Locate the nerve cord. How long is it? How frequently do the ganglia occur on it? Which end of the living worm is the more sensitive. Suggest the connection between this fact and the location of ganglia.
Suggested drawings.
- Earthworm, showing structures mentioned in this study.
Details of Structure—Microscopic Anatomy
Materials.
Sections of earthworms, preferably both cross sections and dorso-ventral, longitudinal ones.
Directions.
In a section under a simple lens, identify the dorsal and ventral surfaces, the body wall, the body cavity, the alimentary canal, and, if possible, the dorsal and ventral blood vessels and the ventral nerve cord.