INTRODUCTION OF THE MICROSCOPE 87 



microscopic structure of plants. Fig. 21 gives a fair sample 

 of the extent to which he observed the cellular construction 

 of vegetables and anticipated the cell theory. While Mal- 

 pighi's research in that field was more extensive, these 

 sketches from Leeuwenhoek represent very well the char- 

 acter of the work of the period on the minute structures 

 of plants. 



His Theoretical Views. It remains to say that on the 

 two biological questions of the day he took a decisive stand. 

 He was a believer in pre-formation or pre-delineation of the 

 embryo in an extreme degree, seeing in fancy the complete 

 outline of both maternal and paternal individuals in the 

 spermatozoa, and going so far as to make sketches of the 

 same. But on the question of the spontaneous origin of life 

 he took the side that has been supported with such triumphant 

 demonstration in this century ; namely, the side opposing the 

 theory of the occurrence of spontaneous generation under 

 present conditions of life. 



Comparison of the Three Men. We see in these 

 three gifted contemporaries different personal characteristics. 

 Leeuwenhoek, the composed and strong, attaining an age 

 of ninety-one; Malpighi, always in feeble health, but direct- 

 ing his energies with rare capacity, reaching the age of sixty- 

 seven ; while the great intensity of Swammerdam stopped his 

 scientific career at thirty-six and burned out his life at the 

 age of forty-three. 



They were all original and accurate observers, but there 

 is variation in the kind and quality of their intellectual prod- 

 uct. The two university-trained men showed capacity for 

 coherent observation; they were both better able to direct 

 their efforts toward some definite end; Leeuwenhoek, with 

 the advantages of vigorous health and long working period, 

 lacked the systematic training ot the schools, and all his life 

 wrought in discursive fashion; he left no coherent piece of 



