EXERCISE 110 



Problem. What are the early stages in the development of a backboned animal from the egg ? 

 What to use. Fresh frog eggs or fish eggs 1 ; magnifiers ; microscope. 

 What to do. Watch the eggs, with unaided eye, with magnifying glass, and with microscope, to 

 note changes that take place from time to time. 



Record. Make drawings to show the stages observed. 



Questions. 1. How does the single cell become a many-celled body? 



2. At what point do the cells appear to be of two or more different kinds ? 



1 If live eggs are not available, make study from models or from charts. 



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