38 



The Medium 



Sinking rate is also controlled in part by size and shape. It might 

 be said that one of the simplest ways of reducing sinking speed is to 

 be small because with reduction in volume the surface— and hence 

 surface friction— becomes relatively greater. Any departure from the 

 spherical shape increases the surface of an organism. Unicellular 

 forms like the pelagic Glohigerina which are bristling with spines 





Bigelow, 1926 

 Fig. 2.6. Marine zooplankton. Photomicrograph of common copepods, chaetog- 

 naths, and medusae. The euphausiid "shrimp" is approximately 2.5 cm (1 in. ) 



long. 



graphically illustrate this fact (Fig. 2.7). Most multicellular animals 

 that live a planktonic life also are liberally provided with long an- 

 tennae, spines, and bristles of a great variety of shapes. The effect 

 of these changes in the morphology of planktonic organisms, com- 

 bined with differences in density, in reducing the sinking rate is il- 

 lustrated in Table 1. 



