NUCLEAR VOLUME AND LIFE-CYCLE OF HYDATINA 287 



male and the female honey-bee I infer that the Kernplasmarela- 

 tion is about the same in both sexes, notwithstanding that the 

 male is presumably haploid. Woltereck ('11) is frankly critical 

 of the appHcability of the Kernplasma theory to the problem of 

 sex determination, particularly, however, in parthenogenetic 

 species. 



7. Age. The relation of nuclear volume to the age of the egg 

 (Herlant) and to the age of the embryo (Eycleshynaer) is men- 

 tioned above under 4. Berezowski ('10) describes a decrease of 

 the Kemplasmaratio in the mouse during the first five months 

 after birth, and Minot ('08) bases an important part of his theory 

 of age and death on the conclusion that a decrease of the ratio 

 K/P not only accompanies but causes senescence. 



8. External conditions. The relative size of the nucleus in 

 various organisms is found to be greater at low temperature than 

 at high, by Erdmann ('08), Hartmann ('19 a), Koehler ('12), 

 Popoff ('08), and Rautmann ('09), and, by inference, Papanicolau 

 ('10), though Rautmann observed that increase of temperature 

 above 20° reversed the change of the ratio in Paramecium, making 

 the nucleus larger, instead of smaller as in the case of increases of 

 temperature up to 20°. With high nutrition Hertwig ('03) ob- 

 served an increase of relative nuclear size in Actinosphaerium and 

 Paramecium, while Morgulis ('11) obtained an increase of K/P 

 with starvation in the guinea-pig, with some discordant results in 

 the rat. Popoff ('09 b) increased the size of the nucleus in 

 Paramecium by means of chemical substances in the water. 

 Absorption of water decreases the K/P relation in the pluteus of 

 Strongylocentrotus (Erdmann, '08). 



9. Depression periods in Protozoa. The periods of depression, 

 common in Protozoa, were found by Popoff ('07) to be accom- 

 panied or preceded by enlargement of the nuclei, and subjecting 

 these Protozoa to certain chemical solutions produced both de- 

 pression and nuclear increase (Popoff, '09 b). A similar conclu- 

 sion is reached by Hartmann ('19 a) for certain Cladocera, in 

 which the periods of depression are said to be characterized by a 

 high K/P ratio. Hertwig ('08) discusses with approval the sug- 

 gested connection between depression and relative nuclear size. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 35, XO. 3 



