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Figure 3. — The 20 chromosomes of an early cleavage in ihe 

 American oyster, Crassoslrea virginica (after colchicine treat- 

 ment). 



Figure 4. — Diagrammatic representation ot'the American oyster. 

 Cidssosliea virgiiilcii. chromosomes based on their lengths and 

 position of their spindle attachment regions. 



I I 



