specialisod among the Cyclo])ranch Docor>lossa, and thereby 

 g'ives evideiK'o of the diftioulty of dio-estiiig the toiigli 

 vegelabh^ food ; tlie hig'h (h^velo})itient of fohls nuist also 

 enable this region of the gut to act as a strainer, preventing 

 tlie further transport of large fragments into the thin 

 walled regions Avhich follow. The great length and size 

 of the stomach, which is the region where the secretion of 

 the gieat digestive gland becomes mixed with the food 

 is a fui'ther testimouy to the slowness and ditficulty of the 

 digestive process. 



Xervot's System axd Sexse ( )rgaxs. 



The nervous system of Patella viih/dta (fig. 2-5) may be 

 considered under three headings. 



(a) The Circumoesophageal ring with its cerebral, 

 pleural and pedal ganglia, and the ]nincipal nerves thence 

 given off except— 



(h) The Buccal and Labial nervous svstems, conned ed 

 to the ring at the cerebral ganglia. 



(c) The Visceral Loop and nerves thence given otT, 

 connected to the ring at the pleural ganglia. 



T he (' i re u m oe s o p h a g e a 1 Iv i n g. This is 

 seen, after exposure of the dorsal surface of the gullet, 

 on pressing apart the gut tissues and body wall in the 

 region of the head and neck. When completely exposed 

 it is observed to be roughly fcnir-sided, the plane of the 

 qua<lrilate]'al sloping doM'nwards and backwards, while 

 its upper and lower sides are curved outwards. The 

 fjuadrangular form of the ring is due to its having accom- 

 modated itself to the outlines of the buccal mass. - Though 

 certain swellings on the ring are lef erred to as ganglia, 

 it must not be supposed that nerve cells are not found in 

 othei' parts, the concentratitrn of these being by no means 

 (■om])lele. 'i'he two u])])cr (■(uners of {]\o (|nadiihil(Mal 



