156 Dr Barry on the Unity of Structure 



Lastly, in the larval development of the Lepidoptera (butterfly, 

 moth), curve A E, there is a resemblance to another grade of 

 the Annulata among which the Aphrodite having, " besides 

 a distinct head, many feet on the ventral side of the segments." 

 Now from this example it is obvious, that not only the four 

 Families of perfect Insects, as well as their larval states, but also 

 those animals with which the latter, respectively, have been com- 

 pared, will be, as it were, all located in the diagram ; and this in 

 the order of their respective degrees of elaboration. The latter, 

 therefore, will be easily remembered. Thus, in the curve of 

 least elaboration, are located not only the gnat and house-fly, but 

 also the leech. In the curve of most complete development, not 

 the butterfly and the moth alone, but the Aphrodite, and others 

 of the same grade in the Annulata. So also of the two other 

 curves. 



It seems as if, with the original design to create organized 

 beings, there had arisen a scheme of more or less complete divi- 

 sion and subdivision, continued down to species, and including 

 in the latter, all individual forms.* 



One of the supposed grand divisions may have included ani- 

 mals ,"( one of the first subdivisions, the type of the Vertebrata ; 

 subordinate to which, and co-ordinate to each other, we have 

 the types of Fishes, Reptiles, Birds, and Mammals. Each of 

 these groups presents its families, each family, genera, each 

 genus, species, and every species has its individual forms. So 

 would the other Classes admit of being referred to subdivisions 

 of the supposed scheme. 



In thus speaking of Classes and other divisions of the animal 

 kingdom, however, we by no means acknowledge the present 

 arrangement to be perfect. The only sure basis for classifica- 

 tion is not structure, as met with in the perfect state, when func- 



* Of the order in which the various beings were called into existence, we do 

 not pretend to speak. 



-f- Another of the supposed grand divisions may have comprehended 

 plants ; and this would explain why the resemblance should be so great, be- 

 tween the simplest forms of both. It is obvious, that an inappreciable 

 shade of difference, between two general and crude structures, might occasion 

 divergence to an almost immeasurable distance, in proceeding to the most 

 highly organized and special states. 



