22 



THOS. H. MONTGOMERY jr. 



true nucleolus ; it differs also from the "karyosomes" found in many cells, 

 which are nothing more than temporarily thickened portions of the 

 chromatin reticulum. At the commencement of the anaphase (Figs. 48, 

 49), before the chromosomes have elongated, all of the latter appear 

 to stain a purplish color, i. e. they are then in the process of chemical 

 transition from the immediately preceding state of pure nucleic acid 

 (staining red with saffranine), to the state of the admixture of plastin 

 to this acid (when they stain violet with gentian violet). On account 

 of their mixed color in the early anaphase it is well nigh impossible 

 to determine whether one of them is stained a deeper red than the 

 others. But when the chromosomes have become more or less elong- 

 ated, all of them stain violet (with increasing intensity of color), ex- 

 cept one, which remains red (saffranine), and by strong light may be 

 easily distinguished from the other chromosomes (Figs. 55, 57, n. 2). 

 This one is the chromatin nucleolus, characteristic for the spermato- 

 cytes. At least one whole chromosome becomes thus metamorphosed ; 

 and it is very probable, judging from my observations, that only one 

 becomes thus changed. This chromatin nucleolus retains in all stages 

 up to the formation of the spermatids its red coloration after the use 

 of Hermann's double stain, and so can be easily distinguished from 

 the true nucleolus as well as from the chromatin of the rest stage 

 and anaphase. The following table represents the staining reactions 

 of these structures ; in it, "resting chromatin" denotes the chromatin 

 in those stages from the anaphase to the rest stage; and "dividing 

 chromatin", the chromatin from the loose spirem stage of the 1st 

 spermatocytes up to the raetaphase of the 2nd spermatocytic division. 



resting 

 chromatin 



dividing | 

 chromatin inucleolus 



chromatin 

 nucleolus 



yolk 



Haematoxyline, eosin 

 Ehrlich-Biondi stain 

 Saffranine, violet 



purple 

 light green 

 blue 



blue 



deep green 



red 



red 

 red 

 light blue 



blue 



green 



red 



red 

 red 

 red 



The chromatin nucleolus appears to undergo the same changes 

 of form as do the other chromosomes , up to about the synapsis 

 {n.2 Figs. 55, 57—64). Then it ceases to elongate, and in the post- 

 synapsis gradually commences to assume a spherical form, which is 

 characteristic for it during the telophase and the rest (Figs. 95—100). 

 When it may first be distinguished in the early anaphase, and also 

 during the synapsis, it lies within the nuclear cavity, not in contact 



