The image is a scientific illustration depicting the embryonic development of various vertebrate animals. It's a grid of drawings showing the stages of development for fish, salamander, tortoise, chick, pig, sheep, and rabbit. The illustration is arranged in three rows, each representing a different stage of development. The first row shows very similar-looking embryos across all species, with a basic tadpole-like form. As you move down the rows, the embryos become increasingly distinct, showing features specific to each animal. Here's a breakdown of the stages for each animal: * **Fish:** Starts as a simple elongated embryo, then develops into a tadpole-like form with a visible tail and developing fins, and finally into a more recognizable fish shape. * **Salamander:** Similar to fish in early stages, but develops external gills and limbs. * **Tortoise:** Early stages resemble the others, but develops a more rounded shell and limbs. * **Chick:** Early stages are similar, but develops a prominent head and beak, and limbs. * **Pig:** Early stages are similar, but develops a snout and limbs. * **Sheep:** Early stages are similar, but develops a head and limbs. * **Rabbit:** Early stages are similar, but develops a head and limbs. Below the grid, there are labels identifying each animal. A caption reads: "Fig. 139. Parallelism in development of backboned animals. The three rows of embryos represent distinct stages of development. In the first row the stages of the different species are very much alike; in each succeeding stage they are more distinctive." The illustration is done in a detailed, black-and-white line drawing style, typical of scientific illustrations from the early 20th century. The background is a pale yellow.