ABSTRACT
Echinoderms have been classified among organisms with single myosincontrol, since myosin-control and actin-control do not operate simultaneously in their muscles as in the majority of invertebrates. Mattisson asked whether or not the normal vertebrate pattern for the terminal oxidative stages of respiration was to be found in lower invertebrates, which may live in extreme environments. As Hill pointed out, it had already been deduced that contraction indicated the formation of a molecular interaction through the muscle substance, whether at the beginning of a tetanus or later, when the tetanized muscle was still capable of redeveloping force after a sudden release. The general nature of the subcellular organization of the myofilaments of echinoderm muscle began to be apparent in the first electron micrographs.
