-----------+--------------------+-----------+---------------- | Q₁₀ for Rate of Segmentation in | Q₁₀ for Rate of Temperature+--------------------+-----------+ Oxidations in |_Strongylocentrotus_| _Arbacia_ | _Arbacia_ -----------+--------------------+-----------+---------------- °C. | | | 3-13 | 3.91 | | 2.18 4-14 | 3.88 | | 5-15 | 3.52 | | 2.16 7-17 | 3.27 | 7.3 | 2.00 8-18 | | 6.0 | 9-19 | 2.04 | 4.7 | 10-20 | 1.90 | 3.8 | 2.17 11-21 | | 3.3 | 12-22 | 1.74 | 3.1 | 13-23 | | 2.8 | 2.45 15-25 | | 2.5 | 2.24 16-26 | | 2.6 | 17.5-27.5 | | 2.2 | 2.00 20-30 | | 1.7 | 1.96 -----------+--------------------+-----------+---------------- It is obvious that the temperature coefficient of the rate of oxidations is remarkably constant, about 2 for 10°, for various temperatures and does not show the variation from 7 or more to 2.2 for Q₁₀ for the rate of segmentation. Kanitz[256] has shown that in a graph in which the logarithms of the segmentation velocities are drawn as ordinates and the temperatures as abscissæ the logarithms form two straight lines which are joined at an angle. According to the law of van’t Hoff and Arrhenius concerning the influence of temperature upon velocities of chemical reactions the logarithms should lie in a straight line. We are dealing therefore in these cases with two exponential curves, one representing in _Arbacia_ the interval 7-13° and the second from 13-26°; in _Strongylocentrotus_ between 3-9° and 9-20°. [256] Kanitz, A., _loc. cit._, p. 123. It was found in these experiments that if measurements of the Q₁₀ of later stages of development are attempted the variations due to unavoidable difficulties become too great to permit an equal degree of reliability in the determinations. The vast importance of this influence of temperature upon the rate of development is seen in the fact that in addition to the food supply the rate of the maturing of plants and animals depends on this factor.