Origin of Electric Tissues of Gymnarchus Niloticus. 179 



the Hnin reticulum, this denser material was more refractive and took more 

 of the chromatic as well as more of the acid counterstains than the homo- 

 geneous material did, I shall adopt Schneider's (31) name of "Linom" 

 for the denser substance and his name of " Hyalom " for the clearer and more 

 homogeneous material. It seems probable from the works of Biitscheli (9), 

 Rhumbler (27), Hardy (35), Wilson (34), Andrews (i), Strasburger (32), and 

 others that these structures of cytoplasm, as seen under the microscope in 

 fixed material, do not represent the exact condition as it exists in life. 

 After reading the pages of my recent work on the electric-motor cells of 

 Torpedo, one can more easily see that the cytoplasmic linom is a structure 

 which depends upon the fixative used as one factor and upon the chemical 

 and physical peculiarities and the contents of this plasma at the time that 

 the fixative is applied, as another set of factors. Its reticular or alveolar 

 arrangement can most certainly be immensely varied, and all these artificial 

 conditions must be very much different from that which obtains in life. 

 Since I have only a few fixed specimens to discuss, over whose earlier prepa- 

 ration I had no control, I shall not try to solve the question of what the 

 structure was during life, but will merely describe the present specimen as 

 it appears. 



The linom of the cytoplasmic layer on the posterior end is very fine and 

 can only be seen with the best lenses and under the best conditions. This 

 holds particularly for the outer portion of the layer, for as we examine 

 the inner portion the reticulum grows larger meshed until, at its point of 

 contact with the fibrillar core, the meshes are quite easily seen. 



The same is true as we examine this layer in a more anterior position. 

 Here all the meshes are proportionately larger, until in the layer, as found 

 covering the extreme anterior surface, the meshes of the linom are visible 

 with ordinary high powers. I do not refer to the vacuoles which are found 

 at various points, for there is a great difference between the largest meshes 

 and the vacuoles, although the vacuole may be derived from, or originate 

 in, an overgrown mesh. The meshes always contain the hyalom, while 

 the vacuoles do not. My definition of a vacuole in this case will be a space 

 in the linom into which the hyalom does not extend. Also, the rounded 

 outline of a vacuole shows a surface tension between its content and the 

 cytoplasm, which does not seem to exist between a mesh of the linom and 

 its contained hyalom. These vacuoles appear to have contained a soluble 

 substance during life, and the hyalom is not soluble in fluids used to prepare 

 the specimen. Such vacuoles are found at various points in the cytoplasmic 

 layer, most often at its outer edge, while the large meshes appear at the 

 inner edge and around the nuclei. The vacuoles become so large and 

 numerous at the anterior end of a stage such as figure 18, plate 6, that the 

 cytoplasm looks like foam containing the nuclei and surrounding the 

 unchanged fibrillar core. 



In addition to this structural basis of linom and hyalom, another very 

 prominent content of the cytoplasm is a series of granules of some material 



