chapter 5

page 102.) "There is, then," he concludes, "as we have

said above, a certain analogy, or rather a certain parallelism, to be established between the embryological development of the Cycloids and Ctenoids, and the genetic or paleontological development of the whole class. Considered from this point of view, no one will dispute that the form of the caudal fin is of high importance for zoological and paleontological considerations, since it shows that the same thought, the same plan, which presides to-day over the formation of the embryo, is also manifested in the successive development of the numerous creation which have formerly peopled the earth." Agassiz says himself in his Preface: "I have succeeded in expressing the laws of succession and of the organic development of fishes during all geological epochs; and science may henceforth, in seeing the changes of this class from formation to formation, follow the progress of organization in one great division of the animal kingdom, through a complete series of the ages of the earth." This is not inconsistent with his position as the leading opponent of the development or Darwinian theories. To him, development meant development of plan as expressed in structure, not the change of one structure into another. To his apprehension the change was based upon intellectual, not upon material causes. He sums up his own conviction with reference to this question as follows:* (* "Recherches sur les Poissons Fossiles" volume 1