Abstract
1. The lampbrush chromosomes of Rana cyanophlyctis have been studied by phase-contrast microscopy.
2. In the fully-formed lampbrush chromosomes, the loops are large and the chromomeres so small as to be barely noticeable. In the post-lampbrush stage chromosomes, the chromomeres are more massive and fewer, whereas there are no lateral loops.
3. Chromonema is always single, but its duality is perhaps indicated by two lateral chromomeres at some positions on the chromonema.
4. Loop bridges have been encountered in some preparations. These arise through accidents of manipulation.
5. The chromomeres react positively to DNA tests, but not the loops and the chromonemata. The loops contain RNA, not found in the rest of the chromosomes.
6. Nucleoli appear to arise chiefly on a middle-size chromosome.
7. The nature of chromomeres, chiasmata and the origin of loops are discussed.
