23. 



be watcJied tlirougli the transparent shell, that these movements 

 are not cornmon. The norrnal function of these m-uscles mil be 

 made apparent later, in connection with the special function of 

 the gills. 



Each plate bears cilia along its ventral margin, and for 

 a short distance along each side, but not over its general surface* 



The cilia between the plates are arranged in lines, 

 one or two lines on each side of each plate. Near the ends of 

 the chittnous rods, the cilia on the edges of the plates disappear, 

 and those between the plates becorne modified, as described by 

 Kellogg for holding the plates together. They do not seem 

 to be hooked, but are very numerous, rather stout, and ^fullV inter- 

 mingle with the cluster on the adjoining plate. The area covered 

 by these cilia is ratlxer limited, and above them the plates are not 

 ciliated. The cilia of the gills seem to drive water between the 

 plates and aid in lowering the gills. 



Each gill has two, rather large bundles of muscles run- 

 ning its entire length, one above, figure 19, ulm, and one below, 

 11m. The lower bundle is somewhat crescent shaped in cross sec- 

 tion, the concave surface being directed upward and forming part 

 -f of the ventral wall of a large blood space, lbs, tiiat is also 



continuous the length of the gills. These longitudinal muscles 



• ( ^ 1 ) 

 were supposed by Mits"akurt , "v^iose material was poorly preserv- 



