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 
samc. 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 of the schools, and all his life 
wrought in discursive fashion; he left no coherent piece olf 
