110 ESSAY ON CLASSIFICATION 



Gymnosperms stand among Dicotyledones, no relation can be traced 

 between the relative standing of living plants and the order of suc- 

 cession of their representatives in past ages. On the contrary, let the 

 true affinity of Gymnosperms with Ferns, Equisetacese, and especially 

 with Lycopodiaceas 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 divi- 

 sions 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 carpels supporting their polyem- 

 bryonic seeds in their axis, are more nearly allied to the anathic 

 Acrophytes with their innumerable spores, than to either the Mono- 

 cotyledones or Dicotyledones; and, if the vegetable kingdom consti- 

 tutes a graduated series beginning with Cryptogams, 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, Equisetaceas, and Lycopodiaceae of 

 the Carboniferous period, followed by the Gymnosperms of the Trias 

 and Jura and the Monocotyledones of the same formation and the 

 late development of Dicotyledones? Here, as everywhere, there is but 

 one order, one plan in nature. 



SECTION XXV 



PARALLELISM 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 far been traced only in isolated cases 

 and have not yet led to a conviction that the character of the succes- 

 sion of organized beings in past ages is such in general as to show 

 a remarkable agreement with the embryonic growth of animals; 

 though the state of our knowledge in Embryology and Palaeontology 



