Embryonic state of the oldest Fishes. 37 



wisli to prove in this place, by a careful discussion of facts, 

 is the truth of the law, now so clearly demonstrable in the 

 series of vertebrata, that the successive creations have under- 

 gone phases of development analogous to those which the 

 embryo undergoes during its growth, and similar to the gra- 

 dations which the present creation shews us in the ascending 

 series it presents when viewed as a whole. We may at least 

 consider it henceforth as proved, that the embryo of a fish 

 during its development^ the class of living fishes in its numerous 

 families^ and the fish type in its planetary history, in every re- 

 spect go through analogous phases, throughout rvhich we can 

 always trace the same creative idea (pensee creatrice), like a 

 thread which guides us everywhere in searching out the con- 

 nection of living beings. The consideration that the fishes of 

 the old red sandstone really represent the embryonic age of 

 the reign of fishes, has even been with me a powerful motive 

 to undertake the examination of these ancient animal remains, 

 as my first Monograph, forming a continuation of my Be- 

 searches; since it was here there existed evident facts to 

 prove the truth of this great law of the development of all 

 living beings. 



Let us first take a rapid glance at the families, the species 

 of which I have determined. Of these there are at least five 

 distinct ones, — the Cephalaspides, the Acanthodians, the Dip- 

 terian Sauroides, the Celacanthes, and the Plagiostomes, if so 

 be that we may consider this great type as a single family. 

 The first four belong to the order Ganoides, and the last to 

 that of Placoides. 



The first remark which occurs to the attentive observer is, 

 that among the numerous species scattered throughout these 

 families, we have not yet found any trace of vertebrae, and, 

 in some, only the apophyses to protect the spinal marrow and 

 the large vessels, though they were equally deprived of the 

 bodies of vertebrae. Assuredly, if these fishes had possessed 

 vertebrae, some of them would have been found among the 

 numerous remains of skeletons which abound in the old red 

 sandstone, in those specimens of the Coccosteus from Ork- 

 ney, in which the tails are so well preserved with their spiny 

 apophyses, their small interapophysiary bones, and fin-rays. 



