HYDROBIOLOGY　　　　　　　　　　　　　　　　　　　　　　　　　Pages

A. K. Heinrich. On the feeding of copepods in the tropical region . . . . . . . 1028

PLANT PHYSIOLOGY

D. M. Guseinov. A stimulant of oil-origin as a means to increase crop capacity 1032
P. M. Prikhodko. Development of leaves and productivity of the root in sugar-beet with usual and widerspacing of plants . . . . . . . . . . . . . . 1035

EXPERIMENTAL MORPHOLOGY

L. V. Polezhaev, L. V. Akhabadze, N. A. Zakharova and V. L. Mantieva. On the regeneration of the heart muscle in mammals . . . . . . . . . . . . . 1039

PHYSIOLOGY

A. G. Ginetsinsky and L. N. Ivanova. The rôle of the system of hyaluronic acid—hyaluronidase in the process of water reabsorption in tubules of the kidney . 1043
N. A. Rokotova and I. M. Gorbunova. On reflectory changes in the motor activity of the intestine whose mucous is acted upon with chemical stimuli and beta-rays . . . . . . . . . . . . . . . . . . . . . . . . . . . 1046
G. T. Semenova. The rôle of the strength of an unconditioned reflex in its influence upon the spinal motor reflex . . . . . . . . . . . . . . . . 1050

PARASITOLOGY

B. E. Karulin and A. A. Pchelkina. Homoiothermal animals — vectors of the causative organism of Q-rickettsiosis Ricketsia burneti . . . . . . . . . . 1054

ERRATUM

In my article, published in DAN, vol. 113, No. 6, 1957 (P. I. Petrov, “Second-order invariants of a quaternary differential quadratic form”), the expressions for $\omega_3$ and $\bar{\omega}_3$ were printed incorrectly. It should read:

[
\begin{aligned}
\omega'_3={}&a_1\left[(c_4^2+c_5^2+c_6^2)(c_7^2+c_8^2+c_9^2)-(c_4c_7+c_5c_8+c_6c_9)^2\right]+\
&+a_2\left[(c_1^2+c_2^2+c_3^2)(c_7^2+c_8^2+c_9^2)-(c_1c_7+c_2c_8+c_3c_9)^2\right]+\
&+a_3\left[(c_1^2+c_2^2+c_3^2)(c_4^2+c_5^2+c_6^2)-(c_1c_4+c_2c_5+c_3c_6)^2\right]+\
&+2a_4\left[(c_1c_7+c_2c_8+c_3c_9)(c_4c_7+c_5c_8+c_6c_9)\right.\
&\qquad\left.-(c_7^2+c_8^2+c_9^2)(c_1c_4+c_2c_5+c_3c_6)\right]+\
&+2a_5\left[(c_1c_4+c_2c_5+c_3c_6)(c_4c_7+c_5c_8+c_6c_9)\right.\
&\qquad\left.-(c_4^2+c_5^2+c_6^2)(c_1c_7+c_2c_8+c_3c_9)\right]+\
&+2a_6\left[(c_1c_4+c_2c_5+c_3c_6)(c_1c_7+c_2c_8+c_3c_9)\right.\
&\qquad\left.-(c_1^2+c_2^2+c_3^2)(c_4c_7+c_5c_8+c_6c_9)\right];
\end{aligned}
]

[
\begin{aligned}
\bar{\omega}'_3={}&b_1\left[(c_2^2+c_5^2+c_8^2)(c_3^2+c_6^2+c_9^2)-(c_2c_3+c_5c_6+c_8c_9)^2\right]+\
&+b_2\left[(c_1^2+c_4^2+c_7^2)(c_3^2+c_6^2+c_9^2)-(c_1c_3+c_4c_6+c_7c_9)^2\right]+\
&+b_3\left[(c_1^2+c_4^2+c_7^2)(c_2^2+c_5^2+c_8^2)-(c_1c_2+c_4c_5+c_7c_8)^2\right]+\
&+2b_4\left[(c_1c_3+c_4c_6+c_7c_9)(c_2c_3+c_5c_6+c_8c_9)\right.\
&\qquad\left.-(c_3^2+c_6^2+c_9^2)(c_1c_2+c_4c_5+c_7c_8)\right]-\
&+2b_5\left[(c_1c_2+c_4c_5+c_7c_8)(c_2c_3+c_5c_6+c_8c_9)\right.\
&\qquad\left.-(c_2^2+c_5^2+c_8^2)(c_1c_3+c_4c_6+c_7c_9)\right]+\
&+2b_6\left[(c_1c_2+c_4c_5+c_7c_8)(c_1c_3+c_4c_6+c_7c_9)\right.\
&\qquad\left.-(c_1^2+c_4^2+c_7^2)(c_2c_3+c_5c_6+c_8c_9)\right].
\end{aligned}
]

P. I. Petrov

T-05030 Signed for printing 19/V—1958. Print run 5400 copies. Order 246
Paper size $70\times108^{1}/_{16}$. Paper sheets $6^{3}/_4$. Printed sheets $18.5+2$ inserts. Publisher’s sheets 18.5

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