ANODONTA. 



273 



supra-branchial chambers from the mantle-cavity below. 

 Posteriorly these lead into the exhalent chamber. The water 

 appears to pass between the gill-filaments directly into the 

 supra-branchial and exhalent chambers, aerating the blood 

 in the gill- filaments in its course. The food-particles appear 

 to pass forward to the juouth^ which is situated just under 

 the anterior adductor muscle. They are assisted by a pair 

 of flat triangular labial palps in each side. From this it is 

 seen that the ctenidia serve the two purposes of alimentation 



Fig. 192. — Dissection of Anodonta p^rom Left Side 

 (Slightly Diagrammatic). 



Aperture of Kidney into Pericardium. 



Digestive Gland. Dorsal I 



Aperture of Digestive * I Artery. | 



Gland into Stomach. 



Ventricle of 

 Heart. Pericardium. 



Pedal Ganglion 



Gonad. 



Poste. iur 

 Adductor. 



Visceral Ganglion. 



Intestine. Kidney. 



(food ingestion) and of respiration. They appear to be 

 derived from organs of the same nature as the gills of other 

 molluscs. 



The mouth leads into a short oesophagus passing into a 

 globular stomach, into which open the ducts of a digestive 

 gland. From the stomach the long intestine de- 

 Alimentary. ^^^^^^ -^^^ ^^ y^^^^ ^f ^^ fQQ^-^ ^^^ after com- 

 plex-coils it again ascends to the dorsal region and passes 

 backwards over the posterior adductor muscle to open by an 

 anus into the exhalent aperture. We may note the entire 

 absence of "head," buccal mass and odontophore. 



M 19 



