Quarterly Journal of Microscopical Science, Vol s3-104, 535-549, Copyright © 1963 by Company of Biologists

The Nerve-Net of a Swimming Anemone, Stotnphia Coccinea

¹ Department of Zoology, Downing St., Cambridge

The nervous system of this anemone has been examined in an attempt to study the pacemaker system, previously thought to be localized in the median zone of the column. No clear-cut nerve-ring has been found. The whole column, however, is characterized by the presence of large multipolar nerve-cells in the endoderm, to which pacemaker activity is provisionally attributed. There are several thousand of these cells and their neurites connect with those of other nerve-cells and sense-cells in the column, and with the mesenteric nerve-nets. The column nerve-net, of which the multipolars form part, conducts slowly and fatigues easily. Present physiological evidence from Stomphia and other coelenterates does not invalidate the suggestion that the multipolar cells may also function as a pacemaker system.

Other features of the nervous and sensory systems are very like those of other anemones (e.g. Calliactis, Metridium). The column, mesenteries, and oral and pedal disks are briefly described; much information is still lacking. As expected, sense-cells are aggregated along the angles of the mesenteries except in the pharynx. Their neurites connect with the column nerve-net, and with the mesenteric nerve-nets. A well-developed network of bipolar nerve-cells on the retractor surface may be regarded as a rapid through-conduction tract. As in Metridium and Calliactis the radial nerve-net on the opposite face of the mesentery is similar but much sparser. The ectodermal surface of the oral disk, as described by the Hertwigs, shows a crisscross network of bipolar nerve-cells together with radial rows of small multipolar nerve-cells above the septa. These might perhaps have a proprioceptive function. In the endoderm of the pedal disk, sense-cells are numerous but nerve-cells few. These features are discussed only in so far as they may be related to the swimming behaviour of Stomphia.