Chap. I. SUCCESSION AND STANDING OF ANIMALS. 107 



SECTION XXIV. 



PARALLELISM BETWEEN THE GEOLOGIC.VL SUCCESSION OF ANIMALS AND PLANTS AND 



THEIR PRESENT RELATIVE STANDING. 



The total absence of the highest representatives of the animal kingdom in the 

 oldest deposits forming part of the crust of our globe, has naturally led to the 

 very general belief, that the animals which have existed during the earliest period 

 of the history of our earth were inferior to those now living, nay, that there is 

 a natural gradation from the oldest and lowest animals to the highest now in exist- 

 ence.^ To some extent this is true ; but it is certainly not true that all animals 

 form one simple series from the earliest times, during which only the lowest types 

 of animals would have been represented, to the last period, when Man appeared 

 at the head of the animal creation.^ It has already been shown (Sect. VII.) that 

 representatives of all the great types of the animal kingdom have existed from the 

 beginning of the creation of organized beings. It is therefore not in the succes- 

 sive appearance of the great branches of the animal kingdom, that we may expect 

 to trace a parallelism between their succession in geological times and their relative 

 standing at present. Nor can any such correspondence be observed betAveen the 

 appearance of classes, at least not among Radiata, MoUusks, and Ai'ticulata, as their 

 respective classes seem to have been introduced simultaneously upon om* earth, with 

 perhaps the sole exception of the Insects, which are not known to have existed 

 before the Carboniferous period. Among Vertebrata, however, there appears already a 

 certain coincidence, even witliin the limits of the classes, between the time of their 

 introduction, and the rank their representatives hold, in comparison to one another. 

 But upon this point more hereafter. 



It is only within the limits of the diiFerent orders of each class, that the paral- 

 lelism between the succession of their representatives in past ages and their respec- 

 tive rank, in the present period, is decidedly characteristic. But if tliis is true, it 

 must be at the same time obvious to what extent the recognition of this corre- 

 spondence may be influenced by the state of our knowledge of the true affinities 

 and natural gradation of living animals, and that until our classifications have become 

 the correct expression of these natural relations, even the most striking coincidence 

 witli the succession of their representatives in past ages may be entirely overlooked. 

 On that account it would Ijc presumptuous on my part to pretend, that I coidd 



* See the palscontological works quoted in Sect. 21. ' Aoassiz, (L.,) Twelve Lect, etc., p. 25 and 69. 



