630 UNITY OF DESIGN. 



highest stations in each series possess, at the 

 commencement of their existence, forms exhibit- 

 ing a marked resemblance to those presented in 

 the permanent condition of the lowest animals 

 in the same series ; and that, during the pro- 

 gress of their developement, they assume, in 

 succession, the characters of each tribe, corre- 

 sponding 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 embry- 

 onic evolution. Another consequence of this 

 hypothesis is that we may expect occasionally 

 to meet, in inferior animals, with rudimental or- 

 gans, 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 sufficiently perfected. The 

 following are among the most remarkable facts 

 in illustration of these propositions. 



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 organiza- 

 tion, from Vermes of the lower orders ; both 

 being equally destitute of, or but imperfectly 

 provided with external instruments of locomo- 

 tion ; both having a distinct vascular circulation. 



