Het Leven der Dieren: Deel 1, Hoofdstuk 05: Robben; Hoofdstuk 06: Insecteneters

The chapter describes seals as four-limbed marine mammals with fore- and hindlimbs modified into flippers, digits often joined by webbing or enclosed in skin, a relatively small head with closable slit-like nostrils, large eyes with a nictitating membrane, reduced external ears, and a short tail; their skeleton and dentition show affinities with carnivores. It surveys worldwide coastal and some inland distributions, highlights exceptional swimming and diving skill used to capture fish through precise fin and neck movements, contrasts this with marked clumsiness on land where locomotion is by body undulation, and characterizes social, often nocturnal colonies that bask by day and may fast during breeding.