252 Royal Society : — - 



several trunks of considerable size, which immediately communicate 

 to form a continuous plexus. The part of the plexus on the inner 

 side is much the larger, and supplies anteriorly, the muscular and 

 mucous coats of the mouth as far as the lips ; and posteriorly, the 

 pharynx and suctorial disc ; uniting in both directions with its fellow 

 of the opposite side. The outer part supplies the muscular bands 

 and salivary tubules. From the pharynx, the plexus descends along 

 the side of the oesophagus, lying on the abdominal vessels, and com- 

 municates with minute filaments from the nerves of the subventral 

 ganglia. 



The whole of this little chain with a large portion of its plexus 

 and the wall of the pharynx on which it lies, was removed and exa- 

 mined under a 4^th-inch object-glass, when a beautiful and unexpected 

 appearance was observed. The under surface of the entire chain — 

 cords as well as ganglia — was covered with a lamina of round, oval^ 

 and pyriform cells ; and on its upper surface a row of cells of the 

 same kind was found along each border. At every point of commu- 

 nication between the branches which form the plexus, a minute gan- 

 glionic enlargement was observed, from which new branches proceeded 

 to form other enlargements of the same kind. Every branch com- 

 municated by loops with those adjacent, and by transverse fibres with 

 those of the opposite side, giving to the ganglionic points a kind of 

 stellate appearance. In these microscopic ganglia, the nerve-cells, 

 similar to those of the chain, were accumulated chiefly about the 

 angles, along the borders, and extended some distance into the prin- 

 cipal trunks ; but very few could be seen in connexion with nerve- 

 fibres, which ran around and between them, however, in an intricate 

 manner. As the plexus extended from the chain, the ganglionic points, 

 diminished in size, while the smaller branches given off from the 

 trunks increased in number, and communicated like a capillary net- 

 work. At the same time the ultimate fibres became paler, flatter,, 

 more parallel, and acquired nuclei like those of cells. This was par- 

 ticularly observed in those distributed to the mucous membrane. The 

 above observations were repeated on nearly forty different specimens. 



On considering the parts which it supplies, this little chain appears 

 to combine the oflfice of a sympathetic with certain other functions 

 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 and Miiller, that in some other orders 



