Gottfried Leibniz wrote about Leeuwenhoek to Louis Bourguet, who was "not persuaded by his hypothesis"

I would not wish to speak as decisively as you do, Sir, when saying that Mr Leeuwenhoek's view is a fable of extravagant proportions.

I am very obliged to you, Sir, for what you have deigned to tell me in favour of Mr Leeuwenhoek, whom I respect greatly. Besides, I by no means intended to offend him when I treated his opinion on spermatic worms as a hollow story. Nevertheless, I am not persuaded by his hypothesis. If I could have easily enclosed my proofs for the propositions I have the honour of sending to you, you would have found in abbreviated form the answer to the objections you have deigned to make to me.