Mendel's Principles of Heredity

Hi there
I have a 1913 copy of Mendel's Principles of Heredity by W. Bateson. There a number of places in the book where it looks like pages have been neatly cut out but they aren't plates and there is no interruption in page numbering. Can anyone tell me why this might be? Thanks

There a number of places in the book where it looks like pages have been neatly cut out but they aren't plates and there is no interruption in page numbering.
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