THE ELECTROCARDIOGRAM OF A STOMATOPOD

Abstract
The ecg of the tubular heart of the mantis shrimp, Squilla oratoria de Haan, was studied. Structural findings are described which confirm Alexandrowicz''s observation. The ecg consists of rapid spike components and slow action potentials. The spikes originate from the median nervous system of this heart, and the slow potential from the muscle. Results of transection experiments on the nerve trunk support the view that the nerve cell of the 13th segment has a dominant role in the pacemaker activity of the heart contraction.