The nuclear membrane, or nuclear envelope, that surrounds the nucleus contains numerous small openings called nuclear pores, which make it porous and allow the regulated movement of materials such as RNA and proteins between the nucleus and the cytoplasm.

Mitochondria are not a jelly-like substance between the cell membrane and nucleus; that jelly-like substance is the cytoplasm, while mitochondria are rod-shaped, membrane-bound organelles suspended within the cytoplasm.

Mitochondria, golgi bodies and ribosomes are located in the cytoplasm, not embedded in the nuclear membrane.

Chromosomes are thread-like structures made of chromatin found inside the nucleus; they do not make up the nuclear membrane itself.

Hence, the answer is that the nuclear membrane surrounding the nucleus is porous, allowing the movement of materials.