4 PROBLEMS OF FERTILIZATION 



ment of this new instrument of investigation and its 

 application to the study of the reproductive substances 

 that furnished the first fundamental advance in the 

 theory of reproduction at the hands of Leeuwenhoek, 

 viz., the discovery of the spermatozoa 1 in 1677. 



This discovery aroused the greatest interest in scien- 

 tific circles; a number of investigators repeated the 

 observations and a spirit of speculation which led to 

 wild flights of the imagination was aroused. Leeuwen- 

 hoek had soon to defend his priority in the matter and 

 to protest against certain very imaginative views. 

 Thus in a letter dated June g, i6g9, 2 he defends his pri- 

 ority and combats the notion that the human form can 

 be observed in the spermatozoa. He inveighs especially 



1 This discovery is sometimes credited to Hamm, described as a 

 student of Leeuwenhoek's. The latter himself describes the occurrence 

 as follows (Phil. Trans., 1678, containing a letter from Leeuwenhoek 

 dated November, 1677) : A certain Professor Cranen, who had frequently 

 visited Leeuwenhoek for microscopical demonstrations, requested by let- 

 ter that he should give Dominus Hamm, a relative of his, some demon- 

 strations of his observations. On his second visit D. Hamm brought 

 in a glass vial some seminal fluid and stated that he had observed 

 living animals in it; Leeuwenhoek confirmed this observation and 

 repeated it many times. In this letter he gives a fair description of the 

 spermatozoa, their form, size, and movements, and stated that he had 

 observed them three or four years previously and mistaken them for 

 globules. He did not at this time speculate as to the meaning of the 

 spermatozoa, but in true scientific spirit began to make comparative 

 observations, and in 1678 he described and figured spermatozoa of the 

 rabbit and frog among others. 



The credit of this discovery seems to me to belong rightly to the 

 investigator whose wide experience in the field of microscopical anatomy 

 and whose scientific acumen enabled him to grasp the possible signifi- 

 cance of the discovery, not to the chance observer who called L-eeuwerj- 

 hoek's attention anew to the subject. 



3 Phil. Trans., Vol. XXI- 



