COMPARISONS. 



With three columns, for Ichthyopsida, Sauropsida, and 

 Rat respectively, answer the following questions: 



(1) Is hair present? 



(2) Do you find true scales or feathers? 



(3) Is there an external ear? 



(4) Do you find anything like gill-slits? 



(5) How many chambers in the heart? 



(6) How many aortic arches? 



(7) Do the aortic arches bend to the right or to the left? 



(8) Is a diaphragm present? 



(9) Do they produce eggs? 



Read the account of the Mammalia (pp. 363 to 392). 



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