ANATOMY OF THE CLAM. 



227 



gills, where the embryos in some species partially develop. 



Impregnation probably takes place within the branchial 

 chamber, the spermatozoa being 

 swept in with the respiratory 

 current, and coming in contact 

 with the eggs as they are dis- 

 charged. 



An excellent general view of 

 the relation of parts to the 

 body -Avails and shell may be 

 seen by hardening a clam, or 

 better a fresh -water mussel, 

 Unio (see Fig. 155, D) in alco- 



Fi g . leo. - Pedal ganglia and oto- hoi, and then making trans- 

 v erse sections. A section can 

 b e fl ^ted off in water and ex- 

 ii aminedwith a lens. The per- 



the pedal muscies.-Drawn by w. K. feet bilateral symmetry of parts 



Brooks. * J 



will thus be seen. 

 The above description will answer for the majority oi la~ 



Fig. 161 Lima hians, flying through the water, its long numerous filaments ex- 

 tended. From Brehm's " Thierleben. " 



mellibranchiate mollusks ; in the oyster (Ostrea) or in A no- 



