In Lampetra planeri the epidermis of adult and ammocoete contains a type of bipolar cell, with numerous microvilli about 1 μm long on the apex, and the base associated with a nerve fibre by bar-type synapses. These multivillous cells can be identified with types found by previous authors. In the ammocoete, they correspond to those previously described as epidermal photoreceptors, which were shown to be innervated from the lateralis nerves; this is consistent with the mode of innervation seen by electron microscopy. A pigment seen in the photoreceptors is presumably represented by an organelle consisting of a tangle of microcylinders or tubules, associated in tetrads. The organelle can be called a sinnet, from its configuration. In adult skin, multivillous cells have a close resemblance to the receptor cells of the end buds of adult lamprey epidermis, but they are not associated with supporting cells.