54 EISEN. [Vol. XVII. 



the nucleus shows that this supposition is not correct. With 

 inferior optical methods it seems as if the nuclear contents had 

 been mixed up into an undefinable jumble of irregular granules 

 or rather blotches of protoplasm. Nearly all illustrations of 

 these nuclei appear as if they had been made under such an im- 

 pression. This appearance may also have been due to improper 

 fixing. In reality the nucleus is made up of numerous very 

 small granules of different sizes, many of them arranged into 

 regular rows, for which I have proposed the name "leaders." 

 These leaders consist of a single row of granules connected or 

 strung on a very thin thread of lighter staining substance. 

 The granules are of two kinds, some darker, others lighter. 



These darker granules are the chromioles described else- 

 where, while the lighter ones are mostly linin granules, though 

 it is probable that many of these lighter granules are also 

 chromioles which have been bleached in the differentiation 

 process. 



Besides these granules we also find in the nucleus several 

 larger bodies of a nucleolar nature, such as I have described 

 under the name of " chromoplasts " and "linoplasts." 



In the later stage of this kind of nucleus the leaders become 

 more pronounced, and the chromioles aggregate into chromo- 

 meres of different sizes, while the chromoplasts become con- 

 nected with the leaders in a more intimate manner than before. 

 The leaders soon contract and change into chromosomes, which 

 divide in accordance with the somatic process of mitosis. 



In this paper I am not able, from want of sufficient material, 

 to give a proper account of this mitosis, and a few words as to 

 the process must suffice. 



The mitosis is of the somatic type with twenty-four chro- 

 mosomes. There are probably about four or five generations 

 of cells in rapid succession. The chromosomes, which are 

 at first of zigzag form, are thrown on the central spindle in 

 the form of F's. There are one or two archosomes at each 

 pole. The chromosomes of the spermatogonia are longer and 

 more slender than those of any of the other cells, and there is 

 thus no difficulty in recognizing these somatic mitoses, even 

 when the cells have been so cut that the chromosomes cannot 



