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support for the supposition that they do, on the general 
ground that some kinds of Entomostraca are known to 
undergo these changes, because it is also well known that 
other kinds do not. 
But a further objection was that low forms of animal life 
are liable to extreme variability, and that the same remark 
is applicable to the lower groups in the higher divisions of 
animals, the argument being that in these cases the 
variability may be so great as to render specific distinctions 
of little or no value. He felt compelled to state that he 
did not admit this excessive variability as a certain fact, even 
in the lowest forms of animal life, until it could be actually 
proved to be true by most careful observation, and even then 
he would apply it no further than to the particular cases in 
which it had been proved ; but as to making it a general rule 
with the lowest groups of the higher divisions of animals, he 
saw not the slightest reason for doing so, and here, more than 
in the former case, the diversity of character in the different 
groups would render it extremely unlikely that what might 
apply to one would also be found to apply to another. Even 
among low forms of animal life such as the Foraminifera, he 
had searched in vain for examples of that extreme variability 
which must necessarily confound specific distinctions, and he 
was sure that every young working naturalist, at all events, 
would agree with him that a conclusion so discouraging to 
exact observations as that suggested by Prof. Williamson, 
ought to be accepted by no one unless he became convinced 
of its truth by his own painful experience. With regard to 
the Foraminifera he had no hesitation in saying that, with 
only a few exceptions, the extraordinary uniformity of 
character in individuals of the same type was a fact that 
must strike every observer. In the cases of Miliolina and 
Polymorphina he would admit there is difficulty, but an 
examination of many of their numerous forms did not suggest 
to his mind that a great tendency to variation, in the ordinary 
