85 



adductor having been suppressed and the foot reduced. 

 Furthermore, the mantle, with its important muscles and 

 sense organs, is innervated chieiiy by the visceral ganglia. 



The fused ganglia lie on the ventral surface of the 

 adductor muscle, imbedded in a mass of connective tissue, 

 and can be generally seen without any dissection (by 

 reason of their yellowish brown colour j, on the right side 

 about 0'5 cm. from the last point of attachment of 

 the visceral mass ; that is, slightly postero-ventral to the 

 opening of the right renal organ. 



Its shape is very striking indeed (see tig. 28 j. There 

 is a large central lobe, which is divided anteriorly by a 

 transverse division into a light yellow posterior part, and 

 an anterior portion which is more deeply pigmented 

 yellow. This anterior darker part is sub-divided into two 

 lobes. Laterally, the central lobe is connected by a 

 depressed region with two crescent-shaped expansions or 

 lateral lobes, practically without pigment. Thus there is a 

 post-central lobe (fig. 28, G. c. I.) — unpigmented except 

 in its anterior margin ; two anterior lobes — darkly pig- 

 mented {G. ant.); and two lateral lobes — unpigmented 

 {G. lat.). 



These compound ganglia are connected with the 

 cerebro-pleural ganglia by the cerebro-visceral connec- 

 tives (fig. 28, Con. c. v.). These arise, as we have already 

 seen, from the lower end of the cerebro-pleural, and at 

 once take a course slightly inward and away from each 

 other. That on the left side passes to the left of the 

 rudimentary retractor muscle of the foot, and then lies 

 along the base of the visceral mass at its sides, between it 

 and the renal organs and closely apposed to the addvictor 

 muscle along the greater part of its course. The two 

 connectives on reaching the visceral ganglion enter it just 

 outside the anterior pigmented lobes, viz., by the anterior 



