GENERAL BIOLOGY 693 



position. Ostwald terms this relation the "size of projection," Size of 

 and has asserted that the velocity of sinking decreases in P'^oJ^ction. 

 proportion to the increase in the size of projection.^ 



These two principles of "specific surface" and "size of 

 projection " have in a most wonderful manner been employed 

 by organisms for the purpose of developing their faculty of 

 floating. First of all, in organisms which cannot lower their 

 specific gravity by depositing fats or absorbing water, we find a 

 dominant tendency to develop minute forms in specifically light 

 waters. In this connection we may note that small radiolarians 

 are found in shallow water, and large ones much deeper, as 



Fig. 503. 

 Calocaianus />avo, Dana. '^ (about -\"-). (From Giesbrecht. ) 



mentioned in Chapter IX., and in Chapter VI. Gran refers to 

 the minute coccolithophoridae of the light oceanic surface-layers. 

 A large " size of projection " is found in countless numbers of 

 crustaceans, especially in warm oceanic waters. The copepoda, 

 for instance, show magnificent devices for enlarging their 

 surface, developing feather, plate, or rod -shaped appendages 

 (see Fig. 503). The surface resistance of these appendages 

 depends on their position in the vertical line, and thus they 

 serve the purpose of vertical locomotion as well. 



Ostwald next points out the necessity of studying in nature 



1 Since this was written Sandstrom has published a paper, " Hydrometrische Versuche," 

 Meddelaiiden frail hydrografiska byraii, Stockhohn, 1912, showing that the velocity of sinking is 

 not exactly proportional to the size of projection, other circumstances, which are not yet clearly 

 understood, also influencing the process. 



