ON THE ANCESTRAL FORM OF THE CHORD AT A. 273 



It is also fairly certain that they were not provided with large-yolked 

 ova, otherwise the mode of formation of the layers in Amphibia 

 could not be easily explained. 



The JMammalia and Sauropsida are probably independent off- 

 shoots from a common stem which may be called the Proto-amniota. 



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B. K. n. 18 



