Less than three weeks after Leeuwenhoek wrote this letter, it was received in London (Birch's History, vol. IV p. 217), where it caused some discussion:
It was observed upon Mr. Leeuwenhoeck's letter of July 16th, that the point, where the animal of the male seed is to be first received, and where it is to be first nourished, is placed in the yolk of the egg; and accordingly, that Mr. Leeuwenhoeck made search for the animal in the yolk of the egg: whereas he ought to have looked for it in the white; which is certainly the first nourishment of the chicken, the colliquamentum being there to be found after twelve hours incubation.
It remained to know, whether Mr. Leeuwenhoeck by the abovementioned point did not mean the cicatricula, which adheres to the yolk of the egg.
Mr. Leeuwenhoeck having hitherto been unsuccessful in tracing the animal, it was desired, that he would examine a greater variety of eggs, and particularly those of a silk-worm.
What about Leeuwenhoek's relationship with the Royal Society?
In the previous Letter 37 of January 22, 1683, he noted that he had not received any copies of Philosophical Transactions for years. Apparently, he did not have a complete set prior to that, either. In this next letter, he wrote:
In my letter of August 14th 1675 I wrote to Mr. Oldenburg that in my opinion the food is crushed in the stomach. But that Gentleman has not published this in print as far as I know.
He was referring to Letter 12. In fact, that letter was published in Philosophical Transactions Vol. X, No. 117 on September 26, 1675. An extract was on pp. 380-385 preceded by an extract from Letter 15 of April 21, 1676 on pp. 378-380. Not knowing that, Leeuwenhoek was even further motivated to publish his letters himself, which he began to do the six months later.
In the last paragraph of this Letter 38, he wrote:
A few days ago I at last received from London the missing Transactions.