Huettner’s presentation of vertebrate embryology is remarkable especially for its illustrations. These images on the printed page often look three-dimensional and provide detail and clarity of each case. He noted that he used line drawings in most cases because they were clearer than more complex alternatives, and they could be colored to highlight selected parts. In the introduction to the book, he advised his reader to use colored pencils or crayons to bring out features of the illustrations, for example, highlighting the germ layers. The book remained in print for more than forty years, which is a very unusual achievement in an active scientific field, and was used as a valuable textbook for embryologists. Huettner's original drawings are deposited in the MBL Archives.