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 Mammalia and Sauropsida are probably independent off- 

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



BIBLIOGRAPHY. 



(249) F. M. Balfour. A Monograph on the development of Elasmobranch Fishes, 

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(250) A. Dohru. DIT Ursprung d. WirbeltMere iind d. I'rincip. <l. Functions- 

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(251) E. Haeckel. Schapfungsgeschichte. Leipzig. Vidn also Translation. 

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(252) E. Haeckel. Antkropogenie. Leipzig. I'ide also Translation. Anthro- 

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(253) A. Kowalevsky. " Eutwicklungsgeschichte d. Amphiosus lanceolatus." 

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(254) A. Kowalevsky. " Weitere Stud. iib. d. Entwick. d. einfachen Ascidien." 

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(256) C. Semper. "Die Verwandschaftbeziehungen d. gegliederteu Thiere." 

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B. K. II. 18 



