LEEUWENHOEK 205 



the sperm was the veritable germ, which was only 

 hatched by the female, and he was ready with argu- 

 ments to prove that the " imaginary ova," ' as he calls 

 them, have little or nothing to do with the first forma- 

 tion of the embryo. He. also believed that he could 

 distinguish two kinds of spermatozoa, which he set down 

 with characteristic boldness as the germs of male and 

 female embryos. 



The Crystalline Lens ^ 



Leeuwenhoek showed that the crystalline lens of 

 vertebrates is composed of many thin laminae, and that 

 fibres radiating from the anterior and posterior poles 

 form a three-rayed star in the lens of mammals. 



Vertebrate Histology 



There is perhaps no mention by earlier writers of the 

 transverse striation of muscles,^ the canaliculi of dentine, 

 the fibres of the crystalline lens, or the cells of the 

 epidermis, but it is hard to speak positively in such 

 cases. Leeuwenhoek describes and figures the epidermic 

 cells of his own skin ; he took the cell- nuclei for the 

 ducts of glands.* 



The Compound Eye ^ 



Hooke, Malpighi and Swammerdam had already made 

 observations upon the compound eye of insects, but 



1 These "imaginary ova" were Graafian follicles. Arc. Nat. (1680). 

 Vol. II, p. 27. 



•^Arc. Nat. (1684). Vol. II, pp. 66-81. 



'Phil. Trans. (1681) ; Anat. (1682) ; Are. Nat. (1683?). Vol. I, p. 45 (2nd 

 pagination) ; Vol. II, pp. 30-1. 



*Epist. physiol., Epist. 43 (1717). Vol. IV, pp. 403-8. 

 = Epist. 83, Arc. Nat. (1694) ; Epist. 35, Ep. phys. (1717). Vol. II, pp. 434-7. 

 Vol. IV, pp. 340-7. 



