THE ACCESSORY CHROMOSOME. 5 I 



27. "To return to the chromatin nucleolus. I give this name 

 in order to express its genetic origin, and to distinguish it from 

 the true nucleolus ; it differs also from the " karyosomes " found 

 in many cells, which are nothing more than temporarily thick- 

 ened portions of the chromatin reticulum. . . . But when the 

 chromosomes have become more or less elongated, all of them 

 stain violet (with increasing intensity of color), except one, which 

 remains red (saffranine), and by strong light may be easily dis- 

 tinguished from the other chromosomes. This one is the chro- 

 matin nucleolus, characteristic for the spermatocytes. At least 

 one whole chromosome becomes thus metamorphosed ; and it is 

 very probable, judging from my observations, that only one be- 

 comes 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 dis- 

 tinguished from the true nucleolus as well as from the chromatin 

 of the rest stage and anaphase. 



28. " The chromatin nucleolus appears to undergo the same 

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

 synapsis. Then it ceases to elongate, and in the post synapsis 

 gradually commences to assume a spherical form, which is char- 

 acteristic for it during the telophase and the rest. When it may 

 first be distinguished in the early anaphase, and also during the 

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

 nuclear membrane ; but at the end of the synapsis it gradually 

 takes up a more peripheral position, so that usually during the 

 synapsis, and always in the telophase and rest, it is closely ap- 

 posed to the nuclear membrane. . . . But in most cells in the 

 synapsis it occurs in the nuclear cavity apart from the chromo- 

 somes. In such cases it is found to be usually rod-shaped, often 

 more or less curved, occasionally even lobular ; but so great is 

 its irregularity in form, that in no two cases does it have exactly 

 the same shape. . . . Afterwards it either gradually shortens up 

 into the ultimate spherical form, or first becomes constricted at 

 one or more points on its surface, showing then a more or less 

 beaded appearance, and then, by division at these points, breaks 

 into a number of unequal fragments, each of the latter sub- 

 sequently rounding off. . . . But it is most probable that at first 



