0. DOBELL 



149 



its recovery from the preceding division. At the second hour, however, 

 the nucleus begins to grow, but it does so more slowly than the cyto- 

 plasm. Accordingly, the karyoplasmic ratio (pj gradually increases. 



P 



In the just divided organism, the "karyoplasmic norm" y^ = 67; but 



after 15 hours' growth this has increased to 100. The period from the 

 2nd to the 15th hour is called by Popoff the "period of functional 

 growth of the nucleus," and at the end of it the karyoplasmic ratio 

 reaches its maximum — the " moment of karyoplasmic tension." During 



Frontonia Uucas. ZS'C. 



Time (hou.rs). ^^ 



Fig. 3. (From Popoff, 1908, modified.) 



17 



the next two hours, the nucleus grows ("division growth") more rapidly 

 than the cytoplasm, so that at the I7th hour the karyoplasmic ratio is 



once more normal ( -^ = 67 j. Division now takes place — each daughter- 



, „ ™ , ,, , 1 • X- P volume of cytoplasm ,-,■ „ . • , 



' Popoff reckons the karyoplasmic ratio as ^,= ^ ; , which is Hertwig s 



A volume of nucleus 



karyoplasmic ratio inverted (§ 30). 



