246 SOME ASPECTS OE CELL-CHEMISTRY AND CELL-PHYSIOLOGY 



(Fig. 1 10, A). As the egg approaches its full size, the chromosomes 

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

 ing-capacity increases (Fig. 1 10, B). They are finally again reduced to 

 minute intensely staining bodies which enter into the equatorial plate 

 of the first polar mitotic figure (Fig. no, C). How great the change 

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

 the chromosomes measure, at most, I2yu. (about ^qVo ^'^•) '^"^ length and 

 \yL in diameter. At the height of their development they are almost 

 eight times their original length and twenty times their original 

 diameter. In the final period they are but 2 yw. in length and i jx in di- 

 ameter. These measurements show a change of volume so enormous, 

 even after making due allowance for the loose structure of the large 

 chromosomes, that it cannot be accounted for by mere swelling or 

 shrinkage. The chromosomes evidently absorb a large amount of 

 matter, combine with it to form a substance of diminished staining- 

 capacity, and finally give off matter, leaving an intensely staining 

 substance behind. As Riickert points out, the great increase of sur- 

 face in the chromosomes is adapted to facilitate an exchange of mate- 

 rial between the chromatin and the surrounding substance; and he 

 concludes that the coincidence between the growth of the chromo- 

 somes and that of the ^%%, points to an intimate connection between 

 the nuclear activity and the formative energy of the cytoplasm. 



If these facts are considered in the light of the known stain- 

 ing-reaction of the nuclein series, we must admit that the follow- 

 ing conclusions are something more than mere possibilities. We 

 may infer that the original chromosomes contain a high percent- 

 age of nucleic acid ; that their growth and loss of staining-power is 

 due to a combination with a large amount of albuminous substance 

 to form a lower member of the nuclein series, perhaps even a nucleo- 

 albumin; that their final diminution in size and resumption of staining- 

 power is caused by a giving up of the albumin constituent, restoring 

 the nuclein to its original state as a preparation for division. The 

 growth and diminished staining-capacity of the chromatin occurs 

 during a period of intense constructive activity in the cytoplasm ; its 

 diminution in bulk and resumption of staining-capacity coincides with 

 the cessation of this activity. This result is in harmony with the 

 observations of Schwarz and Zacharias on growing plant-cells, the 

 percentage of nuclein in the nuclei of embryonic cells (meristem) 

 being at first relatively large and diminishing as the cells increase in 

 size. It agrees further with the fact that of all forms of nuclei those 

 of the spermatozoa, in which growth is suspended, are richest in 

 nucleic acid, and in this respect stand at the opposite extreme from 

 the nuclei of the rapidly growing egg-cell. 



Accurately determined facts in this direction are still too scanty to 



