82 Dr. C. Collingwood on Recurrent Animal Form, 
great weight to external and striking resemblances in form. 
Under these circumstances, therefore, it can be no waste of time 
to inquire what connexion exists between the two, and to attempt 
to point out a cause for agreements of form, in cases where cor- 
responding agreement in structure is wanting. 
Nature is inexhaustible in resources ; and variety is one of her 
greatest charms. It is often said that no two things in Nature are 
alike, and with truth; for the resemblance, whether in outward 
form, or in internal organization, always partakes of the character 
of a near approach, and not of distinct repetition. This is par- 
ticularly the case with form, which varies more, and is more 
simple in its variations than structure ; and it is this which con- 
firms my belief that structure, and not form, is at once the truest 
basis of Systems of Nature, and the safest criterion in cases of 
doubt and difficulty. Thus, an Archetypal animal may agree to 
a certain extent in structure with a vast group of animals, and 
yet may resemble none of them in outward form. 
It cannot be a matter of surprise, considering the number of 
such resemblances existing throughout the animal kingdom, that 
while the study of homologies was making but slow progress, 
and the true affinities of animals were but little understood, the 
real nature of many aberrant forms should have been lost sight 
of in the contemplation of their homomorphice resemblances. 
Who can wonder if Pliny spoke of the Bat as “ the onely bird 
that suckleth her little ones,” in quaint old Holland’s phraseo- 
logy? What malacologist even can feel surprise that, up to 
recent times, the Polyzoan Molluscoids were mistaken for Zoo- 
phytes ? or that Lhuyd, and at one time the illustrious Ellis, 
should have regarded them both in the light of “ remarkable 
sea-plants,” while his predecessor, Baker, had even looked upon 
them as the production of “salts incorporated with stony 
matter”? Who can wonder that, before the time of Savigny, 
the Tunicated Botrylii should have been regarded as Polypes ? 
_ that Linnzus should have placed Teredo among the Annelides ? 
that, before the Mémoire of Dujardin in 1835, the Foraminifera 
should have been classed with the Cephalopodous Mollusca ? 
In all these cases (and others might be brought to swell the list), 
the animals have been raised, or have sunk, from one subkingdom 
to another. 
But, although they were not always recognized as such, the 
existence of recurrent forms in Nature could not be overlooked 
by the framers of systems, inasmuch as they were stumbling- 
blocks, which almost seemed placed in their path to prevent 
the natural arrangement of animals from being too easy a task. 
A too cursory examination has not unfrequently resulted in 
the false location of an animal, only to be detected, and trium- 
phantly exposed, by a succeeding zoologist. 
Lee 
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