358 THE HISTORY AND SCOPE OF ZOOLOGY IX 



an actual transmutative development of lower into 

 higher organisms. Leeuwenhoek discovered the red 

 blood corpuscles of Vertebrates, saw the circulation in 

 the capillaries of the Frog's foot, described the fibrillar 

 structure and cross -striping of muscular fibre, the 

 tubular structure of dentine, the scales of the epi- 

 dermis, the fibres of the lens, and the spermatozoa, 

 these last having been independently discovered at 

 Ley den in 1677 by Ludwig Ham of Stettin. The 

 spermatozoa were regarded by the " animalculists " as 

 the fully formed but minute young which had to be 

 received in the egg, in order to be nourished and 

 increase in size, and were hailed as a decisive blow to 

 Harvey's doctrine of epigenesis and his dictum " omne 

 vivum ex ovo." Albrecht von Haller was the champion 

 of the so-called " evolutionists " in the eighteenth cen- 

 tury, better called "prseformationists." Haller wrote, 

 " There is no such thing as development ! No part 

 of the animal body is made before another ; all are 

 simultaneously created." A corollary of this doctrine 

 was that the germ contains the germs of the next 

 generation, and these of the next, and so ad infinitum. 

 It was calculated that Eve at her creation thus con- 

 tained within her 200,000 millions of human germs. 

 This was the view of the " ovists," who regarded the 

 egg as the true germ, whilst the " animalculists," who 

 regarded the spermatozoon as the essential germ, would 

 have substituted Adam for Eve in the above calcula- 

 tion. These fanciful conceptions containing as they 

 do a share of important truth were opposed by 

 Caspar Friedrich Wolff, who in his doctorate disserta- 



