GERMINAL LAYERS OP THE EMBRYO. 
273 
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(24) R. Remak. ‘Untersucb. iib. d. Entwick. d. Wirbeltbiere,’ 1855. 
(25) Salensky. “ Bemerkungen iib. Haeckels Gastrsea-tb^rie," 
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(27) A. Kolliker. ‘ Entwicklungsgescbicbte d. Menschen u. d. hob. 
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