Quoting a quote with ellipsis

Suppose I am writing an essay and I wish to quote an author, say Mr. X, and that my quote will contain a nested quote, i.e. it will contain some material written by Mr. Y and quoted by Mr. X. Suppose further that Mr. X has omitted part of the sentence(s) written by Mr. Y, replacing the omitted material with an ellipsis. The essay I write will then look something like this:

In his book on some topic, Mr. X says "The crux of the biscuit is the apostrophe; in his book on naturalism, Mr. Y said 'not all mice . . . like green eggs and ham,' proving my point about biscuits."

Should I make any special mark to indicate that the ellipsis in my quotation does not signify my own omission but rather an omission made by Mr. X?

Thanks.