Friends: Whenever feeling happy, sad, or dangerous, remember two things. First, scientific experiments continue to show that human experience is derived from the creation of natural structure. For example, love, disease, and mental worries are the origin of the creation of microscopic structure. Second, the products of human's creation is based on the natural one. That is, the products are the second creation to the natural one. For example, the toys which children are fond of, are the creation based on Earth's resources and deposits while the meaning the toys transfer is originated from human's feelings for the motion of natural structure. However, scientists do not know what is the origin of the natural creation. Laurent Nottale is the first person in human history who gave the fundamental explanation to the natural creation of Solar system, based on his theory of Scale Relativity. This paper is the study on the natural creation of galaxies. For a planar distribution of matter, Jin He and Bo He defined Darwin curves on the plane as such that the ratio of the matter densities at both sides of the curve is constant along the curve. Therefore, the arms of ordinary spiral galaxies are Darwin curves. Now an important question facing humans is that: Are the arms of barred spiral galaxies the Darwin curves too? Fortunately, Dr. Jin He made a piece of Galaxy Anatomy Graphic Software (www.galaxyanatomy.com). With the software, not only can people simulate the stellar density distribution of barred spiral galaxies but also can draw the Darwin curves of the simulated galaxy structure. Therefore, if Dr. Jin He's idea is true then people all over the world will witness the evidence that the arms of barred spiral galaxies are identical to the corresponding Darwin curves. This paper shows partial evidence that the arms of galaxy NGC 5921 follow Darwin curves.