OBSERVATIONS ON THE VARIATIONS IN SIZE OF THE A REGION OF ARTHROPOD MUSCLE

The muscles of three different arthropods, a mite, a fly, and an ostracod, show variations in the length of the A region within a given individual. There is no indication that the observed differences in A band length are related to the functional state of the muscle since little, if any, decrease in the length of the A bands was noted when sarcomeres shortened. The length of the A region was determined by polarized light microscopy and in the case of the mite and the ostracod this measurement was made on intact muscles. It is concluded that the size of the A filaments in an individual can vary in a manner unrelated to immediate functional changes. The I filaments may vary in size, but this could not be clearly demonstrated.     

GLYCOLATE DEHYDROGENASE IN PRIMITIVE GREEN ALGAE

Glycolate dehydrogenase occurs in nine species of the Prasinophyceae. The occurrence of glycolate dehydrogenase in these unicellular flagellated organisms does not correspond to the lines of evolution suggested for the green algae based on glycolate enzymology and the nature of the spindle at telophase of mitosis. It is proposed that the evolutionary divergence of the glycolate enzyme came after the evolutionary divergence of the spindle features in the green algae.