Pericardium or pericardial sac.
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Gaseous atoms and plasmic ions expand in all directions.
 
        
                    
             
        
        
        
Answer:
The cell walls observed by Hooke gave no indication of the nucleus and other organelles found in most living cells. The first man to witness a live cell under a microscope was Anton van Leeuwenhoek, who in 1674 described the algae Spirogyra. Van Leeuwenhoek probably also saw bacteria.
Explanation: