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which in many Invertebrata are entrusted to separate and special 

 centres ; such as the labial, pharyngeal, and visceral ganglia in Ce- 

 phalopodous and Gasteropodous Mollusca, and the separate parts of 

 the stomato-gastric system of insects, which, although derived from 

 different sources, are in intimate communication with each other. 

 The lateral ganglia in insects have the same position as the little 

 chain of Lumbricus, on the side of the pharynx, which, according to 

 Mr. Newport, is supplied entirely by them ; they arise, however, 

 wholly from the cephalic ganglion, while the chain in Lumbricus has 

 just been seen to take its origin both from this and the pharyngeal 

 collar ; but then, in orthopterous insects, the gangliated recurrent 

 nerve, which is always in intimate connexion with the lateral ganglia, 

 arises entirely from the pharyngeal crus ; and the fact has been ob- 

 served by Burmeister, Brandt arid Muller, that in some other orders 

 these two parts, in regard to size, are in the inverse ratio of each 

 other. In Crustacea also, the whole of the pharyngeal, gastric and 

 visceral nerves take their origin from the crura, as was first shown 

 by Audouin and Milne-Edwards. 



The second set of nerves from the pharyngeal collar come off from 

 its posterior half, and communicate with each other by loops before 

 they leave it. The first and largest sends some filaments to the 

 muscular bands of the mouth, upon which they communicate by evi- 

 dent but slight dilatations with the plexus of the pharyngeal chain ; 

 and after supplying the muscles of the anterior segments, are lost in 

 the integument of the lower lip. The rest take nearly the same 

 course. But what is extremely interesting, the roots of this set at 

 least of the first and second branches are continuous across the crus 

 with those of the former set which belong to the pharyngeal chain; 

 and many of their fibres may be traced not only into its ganglia, but 

 through the trunks which proceed from their opposite sides to form 

 the pharyngeal ganglionic plexus ; so that the nerves distributed to 

 the labial muscles and integument of the outer tube, and those which 

 supply the inflected oral and pharyngeal tube, are in direct con- 

 tinuity, not only at their peripheral extremity, but at their roots also, 

 through the common centre which presides over the whole of the 

 digestive apparatus. A similar connexion will be seen to exist with 

 regard to the cephalic nerves. 



The subventral chain is a double cord gangliated at short intervals 



