Twice each day remove the tray of eggs and allow to cool slightly. Once a day the eggs should be turned before the tray is returned to the incubator. _Questions._ 1. Describe the appearance of the shell when the chick is about to come out. In about how many days after you put the eggs in the incubator did you first note this change? You should watch the incubator carefully from the eighteenth day on. 2. What proportion of the eggs hatched? What reasons can you suggest for the failure of some to hatch? Did any which were pipped fail to hatch? If so, break them open and see if you can discover the trouble. 3. How does the chick get out of the shell? How long does it take for it to get out after the shell is chipped? How does a chick look as soon as it has come out of the shell? 4. With what is a chick covered when it is first hatched? How long before feathers begin to develop? 5. How long before a chick needs food? How does it recognize it? _Summary._ 1. What are the two kinds of development? 2. What are the stages in embryonic development? 3. What two general types of postembryonic development as determined by the amount of the food supplied in the egg? #C. PROTECTION AND CARE OF YOUNG# Library Exercise _Materials._ Books and diagrams showing as many methods for the care of young as possible. _Observations._ 1. To what extent is care given to the eggs and young in the case of fish? Is the number of eggs large or small? Contrast this condition with that of the robin. What general conclusion is suggested? 2. Describe the egg-laying habits of five or more of the following: grasshopper, cecropia moth, tussock moth, leaf miner, case bearer, leaf roller, sphinx moth, gall insects, ichneumon flies, spiders, earthworm. How is the developing animal protected in each case? How is food assured? 3. Contrast the method of the honeybee and the solitary wasp as to the method of caring for and feeding the young. 4. Describe the nests of five or more of the following: spider, honeybee, bumblebee, paper wasp, mud dauber, digger wasp. 5. Describe the nests of the following: stickleback fish, sunfish. 6. Describe the nests of ten birds common to your neighborhood. 7. Describe the homes of the following: woodchuck, mole, squirrel, rabbit, muskrat, prairie dog, beaver, bear. 8. In case of birds which of the parent birds builds the nest and cares for the little birds? 9. How are the young cared for in the following cases: crayfish, cyclops, pipefish, Surinam toad? _Summary._ 1. What general methods are there for protecting the young? 2. What various devices for assuring plenty of food for the developing animal? 3. What is the relation between the care given the young and the number of eggs produced? #D. ADAPTATIONS FOR THE PRESERVATION OF THE SPECIES# Review Questions and Library Exercise 1. Show how the sexual method of reproduction tends to produce variations. 2. What is meant by the term _heredity_?