3. From time to time, for perhaps a week, examine the leaves which were scattered where the worms could reach them. Have the worms moved them about at all? If so, where are the leaves left? Have any been eaten, in part or entirely? If so, is there any evidence of selection, either as to the kind of leaf or the portion of leaf eaten? If earthworms select food, what senses would be useful for the purpose? Have you any evidence that earthworms possess such senses? 4. Looking through the dorsal wall, notice the meandering red line, seen more easily in some regions than in others. This is the dorsal blood vessel. How long is it? Where is it wider? Where narrower? Notice its pulsations. How many times per minute does it pulsate? In which direction is the blood forced? Is there a corresponding ventral blood vessel? Place a small worm between two pieces of glass, so that you may see through it more easily, and identify the blood vessels encircling the digestive canal, near the anterior end. These are the so-called "hearts" of the earthworm. If possible, decide in which direction the blood flows through them. 5. The food canal, or alimentary canal, lies underneath the dorsal blood vessel, and is usually easily seen, especially if it is full of food. Notice it when the worm is fully stretched and again when it is contracted. How long is the canal? Why does it wrinkle when the worm contracts? Where does it open to the outside? Why does it need to? 6. Where do you infer respiration must take place in this animal? Why do you think so? What fits this surface for such a purpose? Why does an earthworm seem so uncomfortable when it is too dry? 7. Where do earthworms live? What conditions are necessary in their habitat? 8. When do earthworms usually leave their burrows? Why at that particular time rather than at another? Why does "the early bird catch the worm"? 9. What enemies do earthworms have? How are they protected against these enemies? 10. If you have found egg capsules when collecting worms, describe them. External Morphology of Earthworms _Materials._ Preserved earthworms, the larger the better. _Observations._ 1. In what respects are the dorsal and ventral surfaces alike? In what respects different? Why? 2. Why are the right and left sides alike? 3. In what respects are the two ends alike? In what different? Why? 4. How many somites are there from the anterior end to the girdle? How many under the girdle? How many from the girdle to the posterior end? 5. Where are the setæ located in a somite? How are they distributed over the body? _Suggested drawings._ a. An earthworm, dorsal aspect. b. An earthworm, ventral aspect. c. An outline diagram of a cross section, to show the location of the setæ, the blood vessels and the alimentary canal. Internal Morphology or Anatomy _Materials._