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Fig. 151. DIAGRAMS OF CELL LINEAGE. 



Upper figure is a general diagram showing the standard num- 

 bering system of nemie blastomeres. 



Lower figure is a diagram of cleavage in Rhubtlias bufonis. 

 Roman numerals in the first vertical column indicate number of 

 cleavage. Arabic numerals in first vertical column give total 



number of cells in embryo. Numbers in parenthesis indicate 



number of cells in a given germ line. Broken curves indicate 



corresponding levels of cleavage in the various germinal lines. 

 Original. 



217 



