Anthonie Heinsius wrote to Leeuwenhoek about recent observations of generation

September 10, 1683

In Letter 75 of 16 September 1683 to Anthonie Heinsius, Leeuwenhoek wrote:

I saw from your welcome letter of the 10th inst. that Your Excellency and several Gentlemen found great pleasure in my observations, and was glad to hear this.

Leeuwenhoek was probably referring to observations that he wrote to the Royal Society about the previous July. He had sent a copy of that letter to Heinsius. His letters to Heinsius in May, July, and earlier in September show his concern over how the Royal Society would receive his observations and ideas about generation.

I also received a few days ago a letter from the secretary of the Royal Society in London thanking me on behalf of that Society for my latest observations. Among other things he says that they will be printed in the Philosophical Transactions that the world may share the knowledge of my progress in the discovery of that great mystery, generation.