DERIVED ORGANIZATION 



93 



with, normally, eight macronuclei which are separate and arise by 

 three consecutive divisions of the division nucleus (Fig. 47). 



When first formed these eight nuclei are com- 

 posed of homogeneous chromatin granules simi- 

 lar in size and in staining capacity. After a 

 period of normal growth and activity, and 

 particularly at the approach of a division 

 period, a different type of granules appears in 

 each of the nuclei. These, which I have called 

 the "X granules" (Calkins, 1930), stain in- 

 tensely with iron hematoxylin but disappear 

 entirely, by hydrolysis of the Feulgen tech- 

 nique; furthermore, they stain green with the 

 acid component of the Borrel stain. One of 

 these X granules, usually more prominent than 

 the others, lies in the anterior third of each 

 nucleus. Its substance spreads out in a zone 

 or flat plate extending transversely through 

 the nucleus (Fig. 47, b, c). This plate reacts 

 to stains exactly like the X bodies and disap- 

 pears by hydrolysis in the same way. The 

 nuclear cleft forms just posterior to this plate 

 and the anterior third of each nucleus, viz.: 

 that portion anterior to the cleft is thrown off 

 and disappears in the cytoplasm. Other X 

 granules which may be present are similarly 

 discarded, leaving the bulk of each nucleus 

 with only one type of granule. The process 

 occurs in all eight nuclei at the same time, 

 and after it is completed, the residual " purified " 

 nuclei all fuse to form a single macronucleus 

 which, after condensation, becomes the division 

 macronucleus (Fig. 128, p. 246) . The substance 

 of the X granules thus appears to have a cyto- 

 lyzing effect on the nucleus and is the agent 

 in formation of the nuclear cleft. 



Ivanic (1929) describes two deeply-staining 

 (iron hematoxylin) granules which appear at 

 the ends of the curved macronucleus of Ewplotes 

 yatella. These he interprets as centrosomes, 

 and argues for a premitotic division of the 

 macronucleus. It is more probable that these 

 are X granules marking the beginnings of two 

 nuclear clefts which pass from the extremities 

 of the nucleus to the center where they disappear, as shown by 

 Kidder (1932) in the case of Conchophthirius mytili. Turner (1930) 



Fig. 47.— Uroleptus 

 halseyi. X bodies. 

 Chromatin elimina- 

 tion and nuclear cleft 

 in preparation for 

 division of the macro- 

 nucleus. (Original.) 



