564 UNITY OF DESIGN. 



It is remarked, in further corroboration of these 

 views, that the animals which occupy the highest 

 stations in each series possess, at the commence- 

 ment of their existence, forms exhibiting a marked 

 resemblance to those presented in the permanent 

 condition of the lowest animals in the same series ; 

 and that, during the progress of their developement, 

 they assume, in succession, the characters of each 

 tribe, corresponding to their consecutive order in 

 the ascending chain ; so that the peculiarities which 

 distinguish the higher animal, on its attaining its 

 ultimate and permanent form, are those which it 

 had received in its last stage of embryonic evolu- 

 tion. Another consequence of this hypothesis is 

 that we may expect occasionally to meet, in inferior 

 animals, with rudimental organs, which from their 

 imperfect developement may be of little or no use 

 to the individual, but which become available to 

 some superior species, in which they are suffi- 

 ciently perfected. The following are among the 

 most remarkable facts in illustration of these pro- 

 positions. 



In the series of Articulated Animals, of which 

 the Annelida constitute the lowest, and winged 

 Insects the highest terms, we find that the larvae of 

 the latter are often scarcely distinguishable, either 

 in outward form, or in internal organization, from 

 Vermes of the lowest orders ; both being equally 

 destitute of, or but imperfectly provided with ex- 

 ternal instruments of locomotion ; both having a 

 distinct vascular circulation, and multiple organs of 

 digestion : and the central filaments of the nervous 

 system in both being studded with numerous pairs 

 of equidistant ganglia. In the worm all these fea- 

 tures remain as permanent characters of the order: 



