ANATOMY OF TIIK CLAM. 



247 



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 

 Avith the eggs as they are dis- 

 charged. 



An excellent general view of 

 the relation of parts to the 

 body -walls and shell may be 

 seen by hardening a clam, or 

 better a fresh -water mussel, 

 Unio (see Fig. 161, D) in alco- 

 Pedai ganeiia and ot> hoi, and then making trans- 

 verse sections. A section can 



166.- 



% j3ffj%FfS 



W & f cotmisstf ?o be floated off in water and ex- 



muscles of foot ; h, auditory nerve i, amined With a leilS. The pei'- 

 otocyst ; k, nerves from ganglia to 



the pedal muscles. Drawn iiy vv, K. feet bilateral symmetry oi parts 



Brooks. J 



will thus be seen. 

 The above description will answer for the majority of la- 



Fig. K'i.Lima Mans, flyine; through the water, its long numerous filaments ex- 

 tended. From Brehm's ' Thierleben. " 



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



