The image is a diagram titled 'Fig. 13. WHORLS.' It features a grid of twelve different types of whirl patterns, each labeled with a number (20-30) and a descriptive name. The patterns are drawn in black lines on a yellowed, aged paper background. Here's a breakdown of the patterns: * **20: Small Spiral in Loop** - A small, tight spiral contained within a larger loop. * **21: Spiral in Loop** - A spiral shape enclosed within a loop. * **22: Circlet in Loop** - A circular or ring-like shape within a loop. * **23: Ring in Loop** - A ring shape contained within a loop. * **24: Rings** - Two overlapping ring shapes. * **25: Ellipses** - Two overlapping elliptical shapes. * **26: Spiro-rings** - Two spiral-shaped rings overlapping. * **27: Simple Spiral** - A basic spiral shape. * **28: Nascent Duplex Spiral** - A spiral that is beginning to split into two. * **29: Duplex Spiral** - A spiral that has clearly split into two distinct spirals. * **30: Banded Duplex Spiral** - A duplex spiral with bands or ridges within the spiral arms. The overall style of the image is reminiscent of scientific illustrations from the late 19th or early 20th century, with a focus on detailed line drawings and clear labeling.