“The scope of Hunter's labors may be defined as the explication of the various phases of life exhibited in organized structures, both animal and vegetable, from the simplest to the most highly differentiated. By him, therefore, comparative anatomy was employed, not in subservience to the classification of living forms, as by Cuvier, but as a means of gaining insight into the principle animating and producing these forms, by virtue of which he perceived that, however different in form and faculty, they were all allied to himself. ‘In what does life consist?’ is a question which in his writings he frequently considers, and which seems to have been ever present.”

“At the close of this (20 Jul 1830), and in the beginning of the next year, Goethe turned again to his favorite studies, the natural sciences. At the suggestion of Boisseree, he occupied himself with deeper inquiries into the laws of the rainbow; and also, from sympathy with the dispute between Cuvier and St. Hilaire, with subjects referring to the metamorphoses of the plant and animal world. He, likewise, revised with me the historical part of the "Theory of Colors," taking also lively interest in a chapter on the blending of colors, which I, by his desire, was arranging to be inserted in the theoretical volume.”