144 



GASTROPODA. 



the left side that grows more actively, and this is the reason why the 

 posterior parts (especially the anus and the organs surrounding it) 



c. 



FIG. 60. A-E, Diagrams illustrating the displacement of the pallial complex and the 

 manner in which the asymmetry of the Gastropod body was developed (constructed 

 after BtfascHLi and LANG). The pallial complex shifts first to the right and then for- 

 ward. In E, it has passed the median line, and here the mantle-cavity has sunk in 

 more deeply. The gills grow back and thus sink deeper into the cavity. The heart, 

 auricles and anterior aorta are outlined in red, the intestinal canal in blue, the nerve- 

 ganglia and visceral loop in black, a, anus ; ao, anterior aorta ; eg, cerebral 

 ganglion ; /, foot ; k, gills ; m, mouth ; n, renal aperture ; peg, pedal ganglion ; pig, 

 pleural ganglion ; r, edge of the mantle and shell ; vc, visceral commissure. 



