INTERNAL STRUCTURE OF SALIVARY GLAND CHROMOSOMES IN SCIARA

Abstract

Detailed description of a region near end 1 of chromosome B in Sciara ocellaris is given. The "discs" or "bands" are interpreted as existing in the living chromosome, probably in the form of discs extending through the chromosome, transversely. Visible granules are regarded as distortions or perforations of the discs due, apparently, to interrelations or interactions of chromatic and achromatic materials during coagulation. In different regions of the chromosome achromatic materials show different types of structure in fixed preparations. That this latter differentiation may indicate a qualitative differentiation of protoplasm and be associated with gene differences is cited as a probability. ".... that these characteristics of the achromatic material are largely responsible for the characteristics of the discs (except thickness) in fixed preparations" is indicated. Longitudinal striations or chromonemata are regarded as artifacts having no counterpart in the living chromosome.