xliv 



INTRODUCTION. 



we can hardly, I think, identify it with any form of 

 nerve*. 



iv. The supposed ganglia are not constructed as F. 

 Muller imagined them to be. He overlooked (in com- 

 mon with other observers) the septa, by which the branch 

 is divided into compartments, and by which the ganglion 

 itself is divided into two separate halves. As a matter 

 of fact, the latter is made up of the enlargements of the 

 cord, at the points where it touches the opposite faces of 

 the septum, and appears to have no further significance. 

 The pore or pores in the centre of the septum (as already 



Fig. xviii. 



-ffief 



Portion of a Branch. 

 end. Endosarcal cord. s. Septum, p. Pore, gn. Supposed ganglion. 



explained) allow of the passage of certain threads, which 

 maintain a connexion between the two sections of the 

 cord ; but the two granular masses never come into con- 

 tact. With a true understanding of the structure, the 

 ganglion disappears from the system. 



Further evidence against Miiller's view of the funi- 

 cular tissue may be derived from the study of its general 

 history and of the special functions which it is found to 

 assume. For our knowledge of the latter we are in- 

 debted to Joliet ; and I shall give a brief outline of his 



* See Nitsche, " Ueb. Flustra membranacea," loc. cit. p. f>6. 



