410 



APPLIED BIOLOGY 



(D) Locate oyster's mantle, gills, hinge of shell, position of mouth, 

 and one central adductor muscle which holds the valves closed. 

 Mount and examine microscopically a piece of gill from an oyster 



just opened, using for 

 mounting some of the 

 salt water found inside 

 the shell, and observe 

 the movements of 

 cilia, which produce 

 currents of water. 



Lamellibranchs. 

 All the clams, 

 mussels, oysters, 

 and other mollusks 

 with bivalved 

 shells belong to a 

 This name (from lamella, 



FIG. 143. Ciliated epithelial cells, a, cells with 

 one cilium each ; b, with many cilia; 6 2 is end 

 of view of b 1 ; c, ciliated cells with underlying 

 cells, the whole forming a stratified epithelium. 

 Similar ciliated cells on oyster gills cause move- 

 ment of water. (From Hatschek.) 



class known as Lamellibranchiata. 



plate ; and branchia, gill) refers to the plate-like gills such as 



the clams and oysters have. 



339. Study of Land-Snail. (L) The common European garden- 

 snail (Helix pomatia), sold in markets, and native snails found in 

 damp woods, may be used for study. 

 When imported from Europe the snails 

 are in the hibernating condition with 

 shell sealed by a plate of hardened slime. 

 If placed on damp sod or paper in a 

 warm room, the animal will "come out " 

 of its shell within a day or two, and 

 begin to move and feed. Specimens 

 for study should be allowed to crawl on 

 plates of glass. Observe the following 

 points of structure and habits : (1) foot, 

 and its movements as seen through the 

 glass ; (2) the head, with four tentacles ; 



(3) the position of the spiral shell; 



(4) the collar at the mouth of the shell ; 



(5) the breathing pore in the collar 



(watch its movements) ; (6) the mouth (best seen through the glass 

 from below) ; (7) the eyes at ends of two of the tentacles. Is the snail 

 bilaterally symmetrical ? 



FIG. 144. Diagram of a land- 

 snail (Helix). s, shell ; a, 

 anus ; b, breathing pore 

 opening into the "lung"; 

 r, opening of reproductive 

 organs ; t, four tentacles ; 

 e, eyes at end of longer ten- 

 tacles. (From Parker and 

 Haswell.) 



