230 Papers from the Department of Marine Biology. 



by some fixatives. Thus many substances that are fixed and retained 

 by osmic acid, formaldehyde, alcohol, and chromic acid are either 

 dissolved or lost as an unchanged solution when the cell is fixed in pure 

 sublimate, picric acid, or in Perenyi's fluid. 



Thus when we find an important element, the "paranucleolus," 

 present in Tetronarce that is not to be distinguished so far in Torpedo, 

 and when we find another element the " telonucleolus " in Torpedo which 

 has not been seen in Tetronarce, I believe that both of these elements 

 must be present as a functional material in some form in both of 

 these fishes. The cells are genetically closely related, they are used 

 for the same identical purpose, and are both adult and in normal con- 

 dition, and the apparently missing element in each case must be present 

 in some form, possibly as a solution. For this reason the names applied 

 in the present paper do not seem entirely satisfactory to the writer, in 

 that they do not express the actual functions and chemical constitu- 

 tions of the cell organs of the nucleus. Nor do all of these names 

 permit of satisfactory comparisons being drawn between the nucleoli 

 to which they are applied and to other nucleoli in other cells. It is 

 certain that in this large nerve-cell we have a very high degree of 

 differentiation of the nuclear organs and, apparently, an opportunity 

 to make more exact studies of their identity and function than in any 

 other cell, unless perhaps the egg-cell. And even in this respect the 

 highly differentiated somatic cell such as that under consideration must 

 be carefully studied and its elements traced back to the egg-cell before 

 any general conclusions can be drawn about the meaning of the elements 

 and their various activities in the nerve-cell. 



LITERATURE. 



The normal cell having been carefully studied, particularly as to its 

 nucleus, the literature on the orientation of the nucleolus in Torpedo 

 and experiments made on cells of Torpedo marmorata and Torpedo 

 ocellata was next looked up to find any observations and experiments 

 as to the question of a polarity of its nuclear contents. Such work had 

 been done, mostly by Italian observers, and in particular by Professor 

 Magini of Rome, who first observed a partial polarity of the entire 

 nerve-cell in this fish (24). He examined many specimens of torpedoes 

 at Naples and found that when the animal was killed by a violent 

 death, as cutting by knife (vivisezione) , the plasmosome was always 

 found lying against that side of the nuclear wall which was nearest the 

 axone. He believed at the time that the axone always left the cells 

 in a ventral direction, and that this was therefore always an orientation 

 in the direction of the axone when it was a ventral orientation. 



He found further that the entire nucleus was moved slightly in this 

 same direction through the cytoplasm of the cell and that in conse- 

 quence a crescentic space was left on the side of the nucleus opposite to 



