THE CIRCULAR THEORY EXPLAINED. 821 
This, the student may probably say, is a simple series, 
beginning with birds, and proceeding in a direct line to 
tortoises; but if so, the question arises, which is the 
next class? what animal is there which belongs to a 
class different from that of the reptiles, but which makes 
the nearest approach to a tortoise? The ornithologist will 
immediately point to the penguins. These are indeed 
birds, but they cannot fly; they have feathers, but they 
are so formed as to resemble scales; they have wings, 
but they are transformed into the shape, and perform 
the same office, as the fore-feet of the turtle; both lay 
their eggs, without a nest, upon the sand, and both seem 
out of their natural element when they are upon the dry 
ground. There still is, it is true, a great difference be- 
tween them ; but that is not the immediate question : 
the point we must keep in view is this, what animals are 
we to place after the tortoises? They are preceded by 
the reptiles, but by what class are they followed ? if the 
penguins possess a greater similarity to them than any 
other existing race, then these birds must be placed next 
in succession, and we consequently come back again to 
the first class of animals we commenced with, namely, 
birds ; the series thus forms a circle, and this union 
is expressed when it is said, ‘‘ that the circle returns 
énto itself.” 
(389.) If any one of our readers find a difficulty in 
fully comprehending the mode by which a series of 
animals forms a circle, let him take a straight piece 
of cane, and affix to it, at equal intervals, the fol- 
lowing labels : penguins, birds, quadrupeds, fish, frogs, 
reptiles, tortoises. That with “penguins” will, of course, 
be the first, and that with “tortoises” the Jast. Let him 
then bend the cane into a hoop, the first label and the 
last will thus be brought together without deranging 
the rest of the series ; by this contrivance he will im- 
mediately comprehend what is meant by a “ circle of 
affinity,” ‘‘ a circular succession,” “ the closing of a 
circle,” or “ a circle returning into itself ;”’ all which 
phrases are only different modes of expressing that circu- 
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