Letter 35 of March 3, 1682 Figure 5 | Arcana Naturae Microscopiorum
Oval figures in the blood of a ray, cod and salmon; some of them enclosed in a small space a little, round body or globule.
Ovale figuertgens in het bloet van een rog, cabbeljaeuw, en salm; eenige van binnen in een kleijne spatie beslooten te hebben, een rond bolletge, of globule.
The smaller enclosed bodies are what we now call the nucleus of the red blood cell.
Note that Leeuwenhoek here uses "globule" synonymously with "round body", suggesting that globule refers to any structure that his lens could not resolve sufficiently for him to observe anthing.
