Millimeters 



Figure 1 11. — System of currents along the ridged surfaces 

 of the palps, C. virginica. Currents along the edges of 

 the palps and at the bottom of lateral gutter are shown 

 in heavy long arrows. The current and countercurrent 

 along the ridges are shown by short arrows. Long 

 narrow arrows denote the movements of particles across 

 the palp toward its free edge. Drawn from life. 



the mass is dropped to the surface of the mantle 

 and discarded through the principal discharge 

 area (fig. 90). Tlie currents along the smooth 

 surfaces of the two internal palps (fig. 110) are 

 directed primarily away from the mouth and 

 toward the free edges along the entire length of 

 the palps. There is a much weaker counterciuTent 

 along the central gutter. The material brought 

 by this current reaches the lower lip and may be 

 puslied into the mouth (fig. 11.3). Some of the 

 particles wliich reach the rounded rim of the lower 

 lip drop back to the surface of the palp and are 

 carried away by the principal currents. 



The system of currents on the ridged surfaces 

 of the palps is very complex (fig. 111). There are 



Mill i meters 



10 



Figure 112. — The paths of two particles across the ridged 

 surface of a palp (small arrows), C. virginica. Small 

 particle at the lower part of the diagram fell between 

 the two ridges into the furrow and was carried away by 

 the current along the edge. A slightly large particle 

 (upper half of drawing) settled on the top of a ridge and 

 was kicked from one crest to another until it reached 

 the bottom current of the lateral gutter and was pushed 

 toward the mouth. Drawn from life. 



two major and opposing cmTents along the lateral 

 groove. The bottom cm'rent runs toward the 

 mouth; at a slightly higher level (heavy long 

 arrows) the currents run in the opposite direction. 

 Equally strong currents directed away from the 

 mouth run along the free edge of the palps. 



There are at least three major currents along 

 the inner sm'faces of the palps: (a) from the base 

 across the palp to the edge, (b) in an opposite di- 

 rection from the edge to the base (fig. Ill, short 

 heavy arrows), and (c) slightly weaker currents 

 from the central part of the palps at about 45 

 degrees to the edge (long slender arrows). 



A particle moving along the ridged surface of 

 the palp may follow a very irregular path. Figure 

 112 diagrams the route of two particles which both 

 were pushed away from the surface. One particle 

 (upper part of fig. 112) settled on the edge of a 

 ridge and was pushed by the uppermost cilia from 

 the top of one ridge to the others until it reached 



THE LABIAL PALPS 



117 



