THE ACCESSORY CHROMOSOME. 49 



stained green, indicating that a chemical change takes place in 

 the chromatic substance. But even in such cases the nucleolus 

 was bright red. . . . By this method (Henneguy's) the chromo- 

 somes and nucleoli are stained bright red, the individual chromo- 

 somes being sharply outlined. . . . During the stages shown 

 in Figs. 49, 51,52 (spermatocytes of Cicada], there appears to be 

 a chemical change in the constitution of the chromosomes. By 

 the safranin and victoria-green method the chromosomes stain 

 red, though not so deeply as the nucleoli. At later stages the 

 chromosomes assume a green color, while the nucleoli continue 

 to stain red. In still later stages the chromosomes again take 

 the red. 



20. " One or often two nucleoli are to be seen (spermatogonia 

 of Cicada]. . . . The cells of b (a spermatocyte cyst) each 

 contain one or two bodies which I consider nucleoli, since 

 they react to the stains quite differently from the chromo- 

 somes. . . . The nucleolus then moves to the periphery of the 

 nucleus, and appears meantime to have divided into two portions, 

 one of which passes into the cytoplasm, while the other remains 

 in the nucleus ; later, both parts appear outside the nucleus and 

 on diametrically opposite sides of it." 



21. With this incomplete account, the nucleolus is left by 

 Wilcox. But in a subsequent paper ('96) he takes up the later 

 history of the element and carries it into the spermatozoon. Two 

 paragraphs will give his conclusions. 



22. " The body which appears in the vacuole of the nucleus is 

 rather problematical, both as to its origin and its fate. It ap- 

 pears usually as a rod of deeply staining substance, whose longest 

 axis is in the long axis of the vacuole ; but the rod may have the 

 form of a crescent. 



23. "The tentative conclusion to which I have come with re- 

 gard to this body is, that it represents the nucleolar substance of 

 the nucleus of the spermatid, and that it subsequently passes into 

 the mass of chromatin, with which it becomes homogeneously 

 mingled. My evidence for this is as follows : Very soon after 

 the second division of the spermatocytes a body is seen in the 

 nucleus. It (crcs.) lies at first among the chromatic granules of 

 the nucleus, but is distinguishable from any of the latter by its 



