222 Papers from the Department of Marine Biology. 



tiation of the nuclear mass into at least six or perhaps seven distinguish- 

 able nuclear organs, as well as the large size of the nucleus, makes it an 

 exceptionally favorable subject for study. While some of these struc- 

 tures are easily recognized as the same organs found in other nerve-cells, 

 others can not as yet be so homologized and consequently their names 

 may have to be changed when their real function becomes known by 

 further study. The accompanying pen outline (text-figure 3) will serve 

 to indicate the structures, with the names more or less temporarily 

 applied to them. A more accurate drawing of the nucleus of this cell 

 appears in figure 2, plate 1, as well as in figures 4 to 9, plate 2. 



The contents of this nuclear membrane are at least six in number and 

 will be considered in the normal cell in the following order: (1) nuclear 

 fluid; (2) nuclear achromatin or linin; (3) plasmosome or chief nucle- 

 olus; (4) chromatin bodies or karyosomes; (5) a more or less frequent 

 and unknown body of nucleolar appearance which I shall call tempo- 

 rarily the telonucleolus; (6) the chromatin or perichromatin of Magini, 

 a body which appears to be very closely connected with the chromatin 

 nucleoli and contains a larger number of smaller bodies; (7) the peri- 

 chromosomes, which are scattered through it in a regular order. The 

 paranucleolus found in the nucleus of this cell in Tetronarce will not 

 be described here, as it is not present hi Torpedo. 



The nuclear fluid can be dismissed with but short discussion. It is 

 a questionable factor as an independent unit in the nuclear structure 

 of this cell, and such of it as is not combined with the other elements of 

 the nucleus must be looked upon as a non-vital element. This nucleus 

 was put under the cell-dissecting arrangement of Barber and torn to 

 bits with the glass needles. Under this treatment it was found that 

 the nuclear membrane could be punctured or torn or even removed 

 altogether and that the mass of the nucleus remaining was of jelly-like 

 rather than of fluid consistency. This seems to show the absence of 

 any large quantity of free liquid material during life. On the other 

 hand, some of the best Flemming fixations, when the largest amount of 

 nuclear material was fixed and retained, still showed some fine empty 

 spaces, while in all other fixations much larger empty spaces are present 

 in the nuclei, and these spaces must represent either shrinkage or 

 fluids which have dissolved out. The evidence seems to show that 

 both are true; that some little free and uncombined fluid is present in 

 the nucleus and that this occupies very small spaces that are more or 

 less enlarged by shrinkage of the remaining structures in the process 

 of fixation. 



The viscous, weak-staining, non-chromatic substance or linin of the 

 nucleus will next be considered. This is probably a nucleo-albumen 

 and is of a jelly-like consistency in the live cell. As may be seen in 

 figure 3, plate 2, it is scarcely visible during life, although dark-stage 

 oblique illumination would probably show it more plainly. In the 



