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AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



posterior part of the blastoderm. Many of the lower layer cells 

 here become much flattened and unite to form a thin membrane, 



Fig. 74. SURFACE VIEWS TO SHOW CLEAVAGE IN THE FOWL'S OOSPERM 

 (from Kolliker, after Coste). Cleavage commencing in 1, completed 

 iu 6. 



the endoderm (hypoblast) (Fig. 76, luj). In the hinder part of 

 the area pellucida an opaque longitudinal strip, the primitive 



