Nuclei are everywhere present.
here structures have been observed which resemble nuclei in some of their characteristics.
As before, only true ring nuclei, and not internal anhydrides of aliphatic compounds, will be mentioned.
True ring systems, which possess the characters of organic nuclei, do not come into existence in threeand four-membered rings, their first appearance being in penta-atomic rings.
The nuclei of the original cells persist in the protoplasmic membrane.