C/» GRIFFIN. 



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color is contained in the gigantic nerve-cells of the centers, 

 some of which are large enough to be visible to the naked eye. 



The cerebral ganglion consists of a single triangular mass 

 of nerve-cells, the apex of the triangle being dorsal. The angles 

 of the mass are formed by the principal collections of cells (each 

 of which is a group of loosely aggregated cell masses), while 

 the central portion of the ganglion is less dense. Each buccal 

 ganglion consists of one large, and a dozen or more smaller, cell 

 masses, each quite separate from the others. The broad but 

 short buccal commissure contains no nerve-cells. Each pleural 

 ganglion consists of one large, and several small, cell masses. 



Each of the visceral and parietal ganglia contains several 

 cell masses, while similar groups of cells are scattered along 

 the entire length of the left pleuro-visceral connective; there- 

 fore, there is a continuous series of ganglionic masses con- 

 necting the left pleural and the visceral ganglia. 



The pedal ganglia are each composed of more than a dozen 

 small cell masses. While these extend into the pedal commis- 

 sure, the central part of the latter remains free from them. 

 The pleural commissure contains no nerve-cell masses. The 

 cell masses of the pedal and pleural ganglia are plainly sepa- 

 rated. 



