A liquid drop bouncing on a solid surface can remain in contact for a short time, which is crucial for understanding the efficiency of super-hydrophobic surfaces and improving water-cooling of hot solids. The contact time, τ, depends on the drop's radius (R), impact velocity (V), liquid density (ρ), and surface tension (γ). The Weber number (W = ρV²R/γ) compares the kinetic and surface energies of the drop. High-speed photography enabled precise measurements of τ, which ranged from 1 to 10 milliseconds. The contact time is mainly influenced by the drop's radius and is independent of the impact velocity over a wide range. This finding is consistent with the scaling of the period of vibration of a drop derived by Rayleigh. The contact time is slightly different from the Hertz time because the kinetic energy for a solid is stored in a localized region, whereas in our case it forces an overall deformation of the drop. The brevity of the contact time means that surfactants in a drop can bounce when thrown onto a solid because the contact time is too short to allow the adsorption of the surfactants onto the fresh interface generated by the shock. The contact time should provide a measurement of the dynamic surface tension of the drop. The hedgehog gene is expressed in the ventral midline of the larva of the limpet Patella vulgata, supporting the existence of a similar mechanism for the development of the midline of the nervous system in protostomes and deuterostomes. The midline is an embryonic region that functions in patterning of the adjacent nervous tissue. In insects, the ventral midline is the region from which cells detach to form the ventrally located nerve cords; in vertebrates, the midline is originally located dorsally. During development, it folds inwards and becomes the ventral part of the dorsally located neural tube and is then called the ventral midline, or floor plate. The dorsoventral axis-inversion theory predicts that similar genes should participate in embryonic patterning of the midline region in both protostomes and deuterostomes. Sonic hedgehog is expressed in the midline of the early vertebrate embryo, most prominently in the floor plate of the developing nervous system, where it functions in the differentiation of ventral neural-tube structures and the dorsoventral patterning of adjacent tissues. However, in the protostome insect Drosophila it is not expressed in the ventral midline — instead, it sets up the border between segments. We isolated a hedgehog homologue from the snail Patella vulgata and used it as a probe for in situ hybridization of whole larvae to determine the site of its expression. We obtained a positive hybridization signal in the ectodermal cells of the ventral midline of a 24-hour-old snail larvaA liquid drop bouncing on a solid surface can remain in contact for a short time, which is crucial for understanding the efficiency of super-hydrophobic surfaces and improving water-cooling of hot solids. The contact time, τ, depends on the drop's radius (R), impact velocity (V), liquid density (ρ), and surface tension (γ). The Weber number (W = ρV²R/γ) compares the kinetic and surface energies of the drop. High-speed photography enabled precise measurements of τ, which ranged from 1 to 10 milliseconds. The contact time is mainly influenced by the drop's radius and is independent of the impact velocity over a wide range. This finding is consistent with the scaling of the period of vibration of a drop derived by Rayleigh. The contact time is slightly different from the Hertz time because the kinetic energy for a solid is stored in a localized region, whereas in our case it forces an overall deformation of the drop. The brevity of the contact time means that surfactants in a drop can bounce when thrown onto a solid because the contact time is too short to allow the adsorption of the surfactants onto the fresh interface generated by the shock. The contact time should provide a measurement of the dynamic surface tension of the drop. The hedgehog gene is expressed in the ventral midline of the larva of the limpet Patella vulgata, supporting the existence of a similar mechanism for the development of the midline of the nervous system in protostomes and deuterostomes. The midline is an embryonic region that functions in patterning of the adjacent nervous tissue. In insects, the ventral midline is the region from which cells detach to form the ventrally located nerve cords; in vertebrates, the midline is originally located dorsally. During development, it folds inwards and becomes the ventral part of the dorsally located neural tube and is then called the ventral midline, or floor plate. The dorsoventral axis-inversion theory predicts that similar genes should participate in embryonic patterning of the midline region in both protostomes and deuterostomes. Sonic hedgehog is expressed in the midline of the early vertebrate embryo, most prominently in the floor plate of the developing nervous system, where it functions in the differentiation of ventral neural-tube structures and the dorsoventral patterning of adjacent tissues. However, in the protostome insect Drosophila it is not expressed in the ventral midline — instead, it sets up the border between segments. We isolated a hedgehog homologue from the snail Patella vulgata and used it as a probe for in situ hybridization of whole larvae to determine the site of its expression. We obtained a positive hybridization signal in the ectodermal cells of the ventral midline of a 24-hour-old snail larva