-^?g^::}^ 



Microns 



30 



Figure 105. — Cross section of the smooth side of labial palp of C. virginica. c.ep. — cubical ciliated epithelium; e.c. — 

 large eosinophilic cell; m.c. — mucous cell; m. — muscle fibers; c.c. — vesicular cells of connective tissue. Note the 

 the infiltration of subepithelial layer by mucus and invasion of blood cells. Bouin, hematoxylin-eosin. 



The epithelium rests on a thin basal membrane 

 consisting of connective tissue fibers and muscles. 

 The core of the ridge is made of delicate connective 

 tissue with occasional large vesicular cells con- 

 taining eosinophilic granules. The description of 

 microscopical structure of the palps given al)ove 

 is in agreement with the observations made on 

 various bivalves by previous workers (Leenhardt, 

 1926; List, 1902; Siebert, 1913; Thiele, 1S86; and 

 Wallengren, 1905a, 1905b). 



The palps are well supplied with blood delivered 



through the anterior aorta, pallial artery, and 

 short tentacular artery. The velar artery 

 branches off from the short tentacular artery 

 and runs the entire length of the palp, giv- 

 ing off numerous ramifications. According to 

 vSchwaneke's observation (1913) on Anodonta, 

 tlie blood from the palp is retiu'ned to the heart 

 by the way of the mantle. 



The palps are innervated by the nerve emerging 

 from the cerebral ganglion nd entering the 

 anterior end of the junction between the paired 



THE LABIAL PALPS 



113 



