Published online by Cambridge University Press: 11 May 2009
A spermatophore is defined as a capsule of albuminous matter containing a number of sperm. Among opisthobranchs the families Retusidae, Philinoglossidae, Bullidae, Atydae and Runcinidae are all said to possess a copulatory apparatus which stores sperm and also forms spermatophores (Ghiselin, 1966). Relatively little information exists concerning the structure of the copulatory apparatus or the spermatophore in these groups and practically nothing is known about the copulatory behaviour of the animals and the fate of the spermatophore (Perrier & Fischer, 1914; Ghiselin, 1963, 1966; Thompson, 1976;Beeman, 1977). This paper will focus on the structure of the spermatophore of the cephalaspid Runcina (Kress, 1977). The formation of sperm occurs in the hermaphroditic glands, in a more central position than that of the eggs. These autosperm leave via the common genital aperture which is located laterally to the gills. They travel by means of strong ciliary action, through a seminal groove to the male copulatory apparatus on the right of the mouth. The sperm then moves through the penis and the prostate into a storage sac, the seminal vesicle. For copulation, these sperm are packed into a spermatophore which should presumably be introduced into the common genital aperture but which may be found attached to the mantle or foot, even to animals not yet sexually mature. We have taken this opportunity to study the spermatophore which otherwise might not be easily detected.