Quarterly Journal of Microscopical Science, Vol s3-99, 505-510, Copyright © 1958 by Company of Biologists

The ‘Posterior Lobes’ of Nephtys: Observations on three New England Species

¹ Department of Zoology, University of Bristol

The disposition of the prostomial mucus-glands in Nephtys picta, N. incisa, and N. bucera provides additional evidence that the posterior lobes, which are attached to the supra-oesophageal ganglion of species such as N. californiensis and N. caeca, have been formed by the posterior migration of prostomial epidermal mucus-cells. In N. picta there are few mucus-cells in the prostomium. In N. incisa there are many, and some at the sides of the prostomium occur in clumps and project into the prostomial cavity. In N. bucera there are numerous mucus-cells, but they are massed at the sides of the prostomium and open to the exterior over a narrow zone. The cell-bodies are in intimate contact with the sides of the supra-oesophageal ganglion and lie within the membranes investing the brain. Subsequent evolution of the prostomial mucus-glands has led to the accumulation of their cell-bodies in the posterior part of the supra-oesophageal ganglion in the form of posterior lobes.