No. 3-] THE PROTOZOA AND METAZOA. 72 I 



granules — the ultimate chromatin elements (Figs. 9, 10, and 

 36). These are so fine that one can distinguish them only 

 after the most careful differential staining. At first they 

 are distributed equally throughout the entire nucleus, but even 

 before all of the chromatin of the karyosomes is converted into 

 chromomeres, those which have already formed begin to col- 

 lect in lines extending from the side of the nucleus which lies 

 nearest the sphere, towards the opposite side (Figs. 9, 10, 32, 

 35, and 36). These lines of granules are the beginnings of 

 the chromosomes. The Biondi-Ehrlich solution and the iron 

 haematoxylin with orange G shows them best; the bright lines 

 of chromatin granules show distinctly in contrast to the broad 

 lines of oxychromatin lying between them. In sections 

 stained by the first method (Fig. 10)^ the minute green chro- 

 matin elements can be traced through all stages of chromo- 

 some-formation, from isolated granules of incredibly small size, 

 distributed throughout the nucleus, to the compact chromo- 

 somes directed towards the sphere. The chromosomes next 

 increase in thickness at the peripheral ends, probably by 

 aggregation of the granules, and taper towards the center of 

 the nucleus until at the inner end the threads are no thicker 

 than the single granules (Fig. 11). The tapering of the chro- 

 mosomes is, however, but a passing phase ; later they gradu- 

 ally thicken throughout their entire length and finally become 

 of uniform thickness (Fig. 38). 



Throughout all stages of nuclear activity there is no evidence 

 to show that oxychromatin is being changed into basichromatin 

 or znce versa. The chromatin granules are derived from the 

 karyosomes, and at all stages can be distinguished from the 

 oxychromatin granules by their intense green chromatin stain. 

 The oxychromatin granules, meantime, do not change in size 

 or in staining reaction. They are many times larger than 

 the chromomeres, and during chromosome-formation they are 

 arranged in lines parallel with the chromosomes (Figs. 9, 32, 36). 



' These minute granules are difficult to represent in black and white and Fig. 10 

 represents but poorly the actual preparation. The intense black dots distrib- 

 uted throughout the nucleus and among the larger granules of oxychromatin give 

 a fairly accurate picture. 



