-PF.KMATOGENES1S OF EUCHROMA GIOANTEA. 169 



den-e ma-- - -t" chromatin in one part of the nucleus, the remainder 

 of the nucK-ii- being occupied by a fine network. It sometinu- 

 happen- thai mop- than one of these areas of aggregation de- 

 velop- Figs, i - i s). 



The outline- of the separate chromosomes may be seen, al- 

 though the\ lie very close together. The nuclear network 

 iio\v a parallel arrangement of thread- prepara- 

 to the formation of the spindle (Figs. 17-18). 



A- i- tli- with other members of this order, the small 



lir<>m<>-"ine is separated from the larger by the hr-t divi- 

 -ioii Fig. 2l). In mitosis the w-chromosomes tend to divide 

 -..meuhai later than the others (Figs. 23-25). 



. \tier tli d li\i>ion the spindle fibers persist in the cyto- 



plasm. Ill--, .radiially cca.se to run parallel to each other, 



in. in. .n- or less interlaced, and finally are arranged in 



spiral for: i 26-28). Later they are converted into the 



tail ..I i he -|MTP 'm (.Fig. 32). 



The (hroMiatin "I the s|K-rmatid at first condenses in lar-e 

 measure it ihe -ide .>t the nucleus nearest the spindle fibtr-. 

 but a- tlu laiter 1< --e th< ir regularity of arrangement, the chro- 

 maiin i- di-p<T-ed throughout the network (Figs. 26-27). It 

 M. -\t l.nak- into small fragments which migrate to the center 

 ..! i he nucleus, one mass, however, (probably the heterochro- 

 m.i-. .m. . i. -m. lining distinct from the rest (Figs. 29-32). As 

 the nu. K -u- api-r. -aches maturity, it elongates and the chromatin 

 becomes im. 1\ -i nuilar, although fragments in chain form are 

 (li-iiucui-lial-1. Fig. 33). 



1 Mscussinx OF RKSULTS. 



\ numb r "i \\.-rkers (see Blackman, 1903) have described 



; ir.. matin nucleoli." They occur in a wide variety (jf plant 



an.l animal groups and usually during a [period of growth. In 



enesis and -permatogencsis they may be present in the 06- 

 aiiil -|>ermat.'U"iiia as well as in the later stages. Among the 



up- in which they have been discovered are echinoderms, 

 inolln-c-. arthro|ods, amphibians and mammalian-, al-o in 

 pn -t../. -a and plants. It may prove instructive to compare 

 some "t" the more -triking of these cases with that of 



