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Give a short Account of the Food Canal of the Lobworm. 



The buccal cavity, which has papillae, opens into a short 

 pharynx. This part of the gut is frequently everted. The 

 next portion, the narrow gullet, has a posterior pair of 

 oesophageal glands. The succeeding gastric portion or 

 " stomach " is wide and is covered with " yellow-cells.'* 

 The narrower intestine extends from the end of the 

 " stomach " to the terminal anus. 



The foremost and hindmost parts of the gut are supported 

 respectively by three anterior septa and numerous pos- 

 terior septa of the body cavity ; in the middle portion of 

 the body, where there are no septa, the gut lies free. 



Describe the main Nervous System of Arenicola. 



There is, as in Lumbricus, a ventral nerve cord and a 

 nerve ring ; but there are no ganglia on the cord, and the 

 cerebral ganglia are represented by slight swellings of the 

 ring. 



Indicate the General Course of the Blood Circulation of the 

 Lobworm, mentioning the Principal Vessels. 



The aerated blood is conveyed from the gills to the 

 body' by seven pairs of efferent branchial vessels (from the 

 seven posterior pairs of gills) which enter the dorsal vessel, 

 and by six pairs of efferent branchial vessels (from the 

 six anterior pairs of gills) which enter sub-intestinal vessels. 

 The flow of the purified blood is mainly forwards. 



Impure blood is returned via the lateral vessels to a pair 

 of contractile " hearts " (above the front end of the " sto- 

 mach "), each of which consists of a thin- walled auricle 

 and a muscular ventricle. The blood is pumped by the 

 ventricles into a ventral vessel ; and, flowing backwards, 

 it is distributed to the gills through the thirteen pairs of 

 afferent branchial vessels. 



How does the Lobworm breathe ? 



By means of its thirteen pairs of external gills or branchiae ; 

 small hollow and branched processes, through the delicate 

 walls of which the blood absorbs oxygen from the water, 



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