338 CELL-CHEMISTRY AND CELL-PHYSIOLOGY 



forming the " chromatin " ot Flcmming, is called " basichromatin." ^ 

 Morphologically, the granules of both kinds are exactly alike,- and 

 in many cases the oxychromatin-granules are found not only in the 

 " achromatic " nuclear network, but also intermingled with the basi- 

 chromatin-granules of the chromatic network. Collating these results 

 with those of the physiological chemists, Heidenhain concludes that 

 basichromatin is a substance rich in phosphorus {i.e. nucleinic acid), 

 oxychromatin a substance poor in phosphorus, and that, further, 

 " basichromatin and oxychromatin are by no means to be regarded 

 as permanent unchangeable bodies but may change their colour- 

 reactions by combining with or giving off phosphorus." In other 

 words, " the affinity of the chromatophilous microsomes of the nuclear 

 network for basic and acid aniline dyes is regulated by certain physio- 

 logical conditions of the nucleus or of the cell."'^ 



This conclusion, which is entirely in harmony with the statements 

 of Kossel and Halliburton quoted above, opens up the most interest- 

 ing questions regarding the periodic changes in the nucleus. The 

 staining-power of chromatin is at a maximum when in the preparatory 

 stages of mitosis (spireme-thread, chromosomes). During the ensuing 

 growth of the nucleus it always diminishes, suggesting that a com- 

 bination with albumin has taken place. This is illustrated in a very 

 striking way by the history of the egg-nucleus or germinal vesicle, 

 which exhibits the nuclear changes on a large scale. It has long 

 been known that the chromatin of this nucleus underg^oes srreat 

 changes during the growth of the Qgg, and several observers have 

 maintained its entire disappearance at one period. Rlickert first 

 carefully traced out the history of the chromatin in detail in the 

 eggs of sharks, and his general results have since been confirmed by 

 Born in the eggs of Triton. In the shark Pristiiirus, Riickert ('92, i) 

 finds that the chromosomes, which persist throughout the entire 

 growth-period of the ^gg, undergo the following changes (Fig. 157): 

 At a very early stage they are small, and stain intensely with nuclear 

 dyes. During the growth of the ^gg they undergo a great increase 

 in size, and progressively lose tJieir stainiiig-capacity. At the same 

 time their surface is enormously increased by the development of 

 long threads which grow out in every direction from the central axis 

 (Fig. 157, A). As the Q.gg approaches its full size, the chromosomes 

 rapidly diminish in size, the radiating threads disappear, and the stain- 

 ing-capacity increases (Fig. 157, 5). They are finally again reduced to 

 minute, intensely staining bodies which enter into the equatorial plate 

 of the first polar, mitotic figure (Fig. 157, C^. How great the change 

 of volume is may be seen from the following figures. At the beginning 

 the chromosomes measure, at most, 12 \x (about ttoVo ^^- ) '^^ length and 



^ '94. P- 543- ^^•'••. P- 547- ^^•'"•. P- 54S. 



