112 ESSAY ON CLASSIFICATION. Part I. 



be fully understood without a thorough acquaintance with the fossils and their 

 distribution in the successive geological formations, and that this case exhibits 

 one of the most striking examples of the influence classification may have upon 

 our appreciation of the gradation of organized beings in the course of time. As 

 long as Gymnosperms stand among Dicotyledones, no relation can be traced between 

 the relative standing of living plants and the order of succession of their repre- 

 sentatives in past ages. On the contrary, let the true affinity of Gymnosperms 

 with Ferns, Equisetaceaj, and especially with Lycopodiacese be fully appreciated, and 

 at once we see how the vegetable kingdom has been successively introduced upon 

 earth, in an order which coincides with the relative position its primary divisions 

 bear to one another, in respect to their rank, as determined by the complication 

 of their structure. Truly, the Gymnosperms, with their imperfect flower, their open 

 car^jels, sujjporting their polyembryonic seeds in their axis, are more nearly allied 

 to the anathic Acrophytes, Avitli their innumerable spores, than to either the Mono- 

 cotyledones or Dicotyledones; and, if the vegetable kingdom constitutes a graduated 

 series beginning with Cryptoganes, followed by Gymnosperms, and ending with 

 Monocotyledones and Dicotyledones, have we not in that series the most striking 

 coincidence with the order of succession of Cryptogams in the oldest geological forma- 

 tions, especially with the Ferns, Equisetacete, and Lycopodiacese of the Carboniferous 

 period, followed by the Gymnosperms of the Trias and Jura and the Monocoty- 

 ledones of the same formation and the late develoj^ment of Dicotyledones ? Here, 

 as everywhere, there is but one order, one plan in nature. 



SECTION XXV. 



PABALLELISM BETWEEN THE GEOLOGICAL SUCCESSION OF ANIMALS AND THE EMBRYONIC 

 GROWTH OF THEIR LIVING REPRESENTATIVES. 



Several authors have already alluded to the resemblance which exists between 

 the young of some of the animals now living, and the fossil representatives of the 

 same families in earlier periods.^ But these comparisons have, thus for, been traced 

 only in isolated cases, and have not yet led to a conviction, that the character 

 of the succession of organized beings in past ages, is such, in general, as to show 



^ Agassiz , (L.,) Poiss. foss., q. a., p. 54. — Em- ques principes relatifs h la Classification naturelle 

 bryonic Types, q. a., p. 11. — Twelve Lect., etc., p. 8. des animaux, An. Sc. Nat., 3e ser., 1844, 1 vol. 

 — Edwards, (H. Milne,) Considerations sur quel- p. Go. 



