Structure and Polarity of Electric Motor Nerve-Cell in Torpedoes. 225 



though by surface tension, a condition that probably exists between 

 the vacuole and its surrounding shell of the denser plasmosome material. 



This remaining or peripheral portion of the plasmosome is, as has 

 been indicated, the dense and refrangent portion of the structure. It 

 usually contains in its substance a large number of much smaller " vacu- 

 oles" of about 1 micron in diameter. These are, to all appearance, 

 exactly like the one larger vacuole, except in size, and in one other 

 respect to be mentioned in the next paragraph. 



This thick, refrangent shell of the plasmosome is apparently made of 

 two very similar layers that slightly differ from each other in staining 

 capacity in the various stains used. The inner layer is darker-staining 

 and also thinner. It surrounds the large chief vacuole, but does not 

 extend around from the outer layer; is not sharp, but distinct, and no 

 surface tension appears to exist between the two substances. 



In the smaller plasmosome the vacuoles are not so completely devel- 

 oped and they are all of one size in the smaller bodies, or in the smallest 

 may even be absent or a single vacuole may exist. 



The staining power of this outer part of the plasmosome appears to 

 be a function of its physical rather than its chemical properties. Thus 

 in the regressive stains, as iron hematoxylin, it first appears very black, 

 but when the decolorization is carried past a moderate point the color 

 suddenly comes out, leaving only a light-gray shade, while other 

 chromatic bodies of much smaller size have retained the black color. 

 The stain does not always come out evenly, but often in patches. If 

 the sections are thick the decolorization of the plasmosome may be long 

 deferred, owing to the slowness of diffusion through its thick and dense 

 body rather than to its chemical relation to the stain. 



In connection with the plasmosome another substance exists which 

 is not so easily seen in many preparations, but which came out clearly 

 and undoubtedly in material from Torpedo ocellata that had been fixed 

 in pure sublimate and stained with safranin. This is the thin layer of 

 chromatic material first discovered in other cells and published by M. 

 Haidenhain in 1892. It forms a very thin and somewhat roughened 

 covering of the entire exterior of the plasmosome and can very easily 

 be overlooked in many specimens because it is either obscured by the 

 total staining of the plasmosome, or if the plasmosome is decolorized 

 enough to be clear, this chromatic shell is also decolorized. If looked 

 for with care and in such a preparation as the above it comes out with 

 entire clearness. 



The morphological position of the plasmosome is the principal object 

 of study in this work and will be considered after this general descrip- 

 tion of the nucleus and before and together with the experimental work. 



The peculiar body which I have only recently found in the nucleus 

 of Torpedo ocellata, and which I shall call temporarily the telonucleolus, 

 is next to be described. This structure is only to be found in a com- 



