286 A. FRANKLIN SHULL 



for a few hours after division in Paramecium and Frontonia, 

 followed by an increase up to the time of the next division, and 

 held that cell division occurred when the ratio K/P had increased 

 to a certain value. 



4. Embryonic development. Godlewski ('08) found that in 

 Echinus the nucleoplasma ratio increases greatly up to the 64-cell 

 stage, but changes little after that, and Koehler ('12) reports a 

 similar increase in Strongylocentrotus. In Crepidula Conklin 

 states that this increase during segmentation is less than has been 

 supposed. Eycleshymer ('04) demonstrated a decrease of K/P 

 during embryonic development of Necturus, and Child ('15) 

 points out that as a rule differentiated cells have relatively smaller 

 nuclei than embryonic cells. Herlant ('17) found that in the 

 artificially activated sea-urchin egg there are two periods of 

 increase of K/P, separated by a period of decrease, and that the 

 accessory treatment must be applied during one of the periods of 

 increase if segmentation is to be caused. 



5. Regeneration. Godlewski ('10), Metcalf ('15), and Suther- 

 land ('15) describe an increase of the Kernplasmarelation in 

 regenerating tissue, though in some cases the increase was pre- 

 ceded by a short period of decrease or of fluctuation. 



6. Sex. Hertwig ('03) calls attention to the striking difference 

 between the low nucleoplasma ratio in eggs and the high value of 

 that ratio in spermatozoa, and sees in this difference a cardinal 

 distinction between the sexes. Sexual dimorphism is attributed 

 by him to the same difference. From the statements of Oeh- 

 ninger ('13) concerning the absolute sizes of the nuclei in the 



volume in the numerator of the fraction (K/P). Eautmann explains that it is more 

 convenient to reverse the terms, since on Ilertwig's plan the value is nearly always 

 a fraction. The other four authors offer no explanation of the reversal, nor do 

 they indicate that they are aware that they have reversed the terms. Decision 

 as to the relative value of these two formulas for the Kernplasmarelation should 

 depend on whether it is the nucleus or cytoplasm that is most active in changing 

 the value of the ratio. If, as most investigators who attach any importance to 

 this ratio of volumes hold, the active changes are chiefly if not exclusively due to 

 changes of the nucleus, the formula of the ratio should be such that the value 

 would increase as the nuclear volume increases. This can be done only by placing 

 the nuclear volume in the numerator, thus, following Hertwig, K/P. In this 

 paper the confusion resulting from the two opposed practices is obviated by trans- 

 lating all conclusions in terms of the formula K/P. 



