302 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



That the Royal Society were appreciative of Leeuwenhoek's great 

 services to science is shown by the fact that in 1G79 a certain Mr. 

 Hunt was " instructed to prepare a silver box for the diploma to be 

 sent to Mr. Leeuwenhoek." 



In 1G80 Leeuwenhoek addressed to the Royal Society a communi- 

 cation headed "De Fermento Cerevisiae," in which he announced 

 that he had discovered that yeast consisted of small ovoid globules. 

 Of these, which he api^eared to regard as consisting chiefly of batches 

 of six, he gives several excellent drawings. When we remember 

 the nature of the magnifying apparatus w^ith which he had to work, 

 and that the average diameter of the yeast-cell is only y^^ millimeter 

 (^-^ inch), it will, I think, be realized that Leeuwenhoek had 

 accomplished a very remarkable feat. He did not, however, push 

 the discovery any further, and in this position, curiously enough, 

 the matter remained for more than a century. 



In the year 1814 Kieser, in the course of a paper by Dobereiner, 

 described yeast as consisting of small spherical corpuscles, but this 

 statement does not appear to have attracted attention, and about the 

 year 1837 the microscopical character of yeast was again made the 

 subject of investigation, and the true nature of the yeast organism 

 was dotinitely and independently discovered by three observers, Cag- 

 niard de Latour, Schwann, and Kiitzing. These observers recognized 

 that yeast is composed of a vast number of small transparent glob- 

 ules which reproduce by budding and which consist of a cell wall 

 with granular contents. A year or two later Schwann appears also 

 to have observed the formation ©f ascospores. These observers, and 

 Cagniard de Latour in especial, put forward the view that it was 

 owing to the vegetation of these cells that the disengagement of car- 

 bon dioxide gas and the formation of alcohol were due. The re- 

 searches of these observers having shown that yeast consisted of a 

 lowly vegetable organism, capable of reproducing by budding, the 

 question arose, how w^as yeast originally formed, and around this 

 subject, as is well known, a fierce scientific controvers}'^ raged, the 

 Heterogenesists, on the one hand, upholding the doctrine of sponta- 

 neous generation, and the Biogenesists, on the other hand, asserting 

 that all life must be derived from preexisting life. With this aspect 

 of the matter, and with this controversy I do not propose on this 

 occasion to deal, and it will suffice perhaps to say that the rigid 

 experiments of Pasteur succeeded in proving to the satisfaction of 

 practically the whole scientific world that every yeast cell was de- 

 rived from a preexisting cell of the same kind, and that the doc- 

 trine of spontaneous generation was not based upon any foundation 

 of fact. 



