mitochondrion

noun

1. A spherical or ovoid organelle found in the cytoplasm of eukaryotic cells and containing genetic material separate from that of the host; it is responsible for the conversion of food to usable energy in the form of ATP.

   “The consideration of the mitochondrion in the spermatocytes I shall pass over, as it is not within the bounds of this paper; yet I hope to study the earlier generations of my material, and shall then compare the results.”