ELECTRIC TISSUES OF ELASMOBRANCHS 1 1 1 



farther down into the papillae, and larger areas are isolated from these 

 main masses. 



The nuclei are found in all three layers, forming a very regular, close- 

 set arrangement in the electric layer, very sparingly scattered through the 

 striated region, and numerous, but irregularly arranged, in the nutritive 

 layer. The nuclei of this last region seem somewhat smaller, more 

 irregular in outline, and with denser chromatin masses than those 

 found in the other layers. Each is surrounded by a mass of granu- 

 lar cytoplasm. These masses are connected and form a separate 

 layer. 



The above section that we have been studying is a longitudinal, 

 vertical section of the spindle, and consequently a longitudinal section 

 of the electroplax. The material was fixed in Flemming's strong fixative 

 and stained in iron-haematoxylin. In order to proceed farther with an 

 understanding of the tissue it will be necessary to prepare other fresh 

 material with Golgi's quick silver method and to cut sections at right 

 angles to the anterio-posterior axis of the electroplax. The sections will 

 be parallel to the neuro-electric surface, the flat surface on which the 

 nerve terminates in many fine branches. When such sections are 

 examined as include all or any portion of this surface, we can distinguish, 

 in favorably stained parts of the specimen, the following facts : 



The ground substance of the electric layer forms a coarse network, 

 whose regular rounded meshes contain the nuclei. Each nucleus is sur- 

 rounded by its own portion of unspecialized cytoplasm, and a thin layer 

 of the ground-substance covers the top and bottom of each mesh with a 

 delicate layer. Thus each nucleus, with the unspecialized cytoplasm 

 that surrounds it, is inclosed in an oval space entirely within the electric 

 layer. 



The ground-substance shows a distinct reticulum or network of 

 fibrils. This network is very fine and dense and stains brown-black. 

 Its fibrils are irregular and granular, and at times can be seen to run some 

 considerable distance without anastomosing. The reticulum is coarser 

 in some regions than in others, and this is so marked that we may dis- 

 tinguish between a fine and a coarse reticulum. 



How far does this reticulum extend into the substance of the elec- 

 troplax and what relation has it to the striations? A cross section of 

 the silver material will show this, and in it we see that it pervades the 

 ground-substance and is found between the striations or lamellae only. 

 Thus it is not directly continuous in the electroplax. 



A remarkable feature that is revealed by the silver process is the mul- 

 titude of tiny pointed rods projecting from the inner surface of the elec- 

 trolemma into the electric layer for a distance of several microns. These 

 structures are very dense and refractive and are only found on that part 



