(-1)\^[\_1-\_3]{}\_1 g\_[-\_1-\_3]{}(t), \[eq:giraffe\] with \_1 = \_1\_3(-1)\^[S\_1-S\_3]{}P\_i\_i, \[eq:hedgehog\] where $S_1$ ($S_3$) and $\eta_1$ ($\eta_3$) are the spin and parity of the particle 1 (3) respectively, and $P_i,\sigma_i$ are the parity and signature of the Reggeon $i$. The vertices behave as [@a12; @a13], g\_[\_1\_3]{}(t) \~(-t)\^[| \_1 - \_3|/2]{}, t0. \[eq:iguana\] Note that relation [(\[eq:giraffe\])]{} depends only on the product $P_i\sigma_i$ and thus the model-independent spin structure of the vertices $g_{\lambda_1\lambda_3}(g_{\lambda_2\lambda_4})$ is the same for all Reggeons with the same product $P_i\sigma_i$.

Below we will be interested mainly in the spin structure of the central vertex $g_{ik}^{\lambda_h}(t_1,t_2,\phi)$. It can be written in the form [@a11] g\_[ik]{}\^[\_h]{} = \_[m\_2 = -]{}\^e\^[im\_2]{} \_[m\_1m\_2]{}\^[\_h]{},m\_1 + m\_2 = \_h, \[eq:jackal\] where $m_2$ has the meaning of the projection of the angular momentum $j_k$ of Reggeon $k$ (analytically continued from all angular momenta $j_k$ in the $t_1,t_2$-channels). Now invariance under parity leads to the relation [@a11] \_[m\_1m\_2]{}\^[\_h]{} = (-1)\^[\_h]{}\_3 \_[-m\_1-m\_2]{}\^[-\_h]{}, \[eq:koala\] where \_3 = \_h(-1)\^[S\_h]{}P\_i\_iP\_k\_k. \[eq:lion\] Thus the spin structure of the central vertex depends only on the product of the naturalities (that is the parities and signatures) of particle $h$ and the exchanged Reggeons[^3]. The behaviour of $\gamma_{m_1m_2}^{\lambda_h}$ for small $t_1,t_2$ is given by the formula 