Introduction to Animal Morphology. 245 



are called pedal ganglia. Two long (sympathetic r) 

 nerves, arising from the oesophageal ganglion, may- 

 unite posteriorly to form a parieto-splanchic or anal 

 ganglion. vSense-organs may exist as tentacles, 

 ciliated smell organs, eyes, otocyst, &c. 



The digestive canal never communicates with the 

 body cavity, and is more or less looped, so that the 

 anus is often near the mouth, and always near the 

 breathing cavity. The intestine is sometimes attached 

 to one or more rudimental transverse partitions, 

 traces of the metameric septa. There are often dental 

 organs, sometimes a crop, always a liver. The circu- 

 lation is lacunary ; the blood clear (rarely coloured). 



Fig- 31- 



A, segrment of the dorsal vessel of a Worm ; i, i, i, inferent vessels ; 2, cephalic end ; 

 2', abdominal end. B, heart of Nautilus ; i, i', auricles ; 2, cephalic aorta ; 2', abdo- 

 minal aorta. C, heart of Lamellaibranch or Loligo. D, heart of Octopus. E, heart 

 of Gasteropod. 



corpusculated, and propelled by a heart, which re- 

 sembles a segment of the circulatory system of worms 

 (Fig. 31), receiving blood from one or two pairs of 

 dilated, transverse vessels distended into auricles, or 

 rather into dilated, branchial sinuses (Fig. 31, i, i'), 

 which receive blood from the gills, and empty it into 

 a longitudinal dorsal vessel, modified into a ventricle, 

 usually straight, rarely flexed on itself, and sending 

 forward a cephalic (Fig. 31, 2), and backwards an 



