168 ESSAY ON CLASSIFICATION. 



standing of living plants and the order of succession of their 

 representatives in past ages. On the contrary, let the true 

 affinity of the Gymnosperms with the Ferns, Equisetacese, 

 and especially with the Lycopodiacese, be fully appreciated, 

 and we at once 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 deter- 

 mined by the complication of their structure. Truly, the 

 Gymnosperms, with their imperfect flower, their open 

 carpels supporting their polyembryonic seeds in their 

 axis, are more nearly allied to the ananthic Acrophytes 

 with their innumerable spores than to either the Mono- 

 cotyledones or Dicotyledones ; and if the vegetable king- 

 dom constitutes one graduated series, beginning with the 

 Cryptogams, followed by the Gymnosperms, and ending with 

 the Monocotyledones and Dicotyledones, have we not in 

 that series the most striking coincidence with the order of 

 succession, as exhibited by the Cryptogams of the oldest 

 geological formations, especially the Ferns, Equisetacese, 

 and Lycopodiacese of the Carboniferous period, followed 

 by the Gymnosperms of the Trias and Jura and the Mono- 

 cotyledones of the same formation and the late develop- 

 ment of the Dicotyledones I 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 REPRE- 

 SENTATIVES. 



Several authors have already alluded to the resemblance 

 which exists between the young of some of the animals 



