58 



T. navalis. This fiprure also s>iows the distribution of 

 the pland in the branchial vein, and that this portion is 

 ol" the same nature as that lying in the lamina adjacont to 

 it. Still farther from the vein, is tlie second typo of 

 structure. Ramifying in all directions from the latter 

 are dendritic processes, which penetrate the epithelial 

 walls of the lamina. These ramified portions are the pri- 

 mary structures, and the other two are derived from them. 

 The structure of the dendritic portion is shown in figs. 

 47 ,48, which were drawn vrnder a magnification of 1900 di- 

 ameter. The processes seem devoid of any membrane. The 

 contents consist of very minute filamentous structures ar- 

 ranged lengthwise in the direction of the process. Lying 

 i-n the mass thus formed are nuclei v/hich vary in niamber 

 and position. The middle one in fig. 48 indicates that 

 they may change position, and that the whole structure 

 forms a sincytiiom. The enlarged portions of the processes 

 shovm in fig. 37, became surrounded by an epithelial cov- 

 ering, apparently derived from the lining cells of the 

 lamina. This stage is represented in figs. 46 and 47. 

 The minute filamentous structures have taken on a more ir- 

 regular arrangement, and lying within the mass; are spher- 



