240 BIOGENESIS AND ABIOGENESIS vill 



on to ask how far the growth of science justifies 

 his other hypothesis of Xenogenesis. 



The progress of the hypothesis of Biogenesis 

 was triumphant and unchecked for nearly a 

 century. The apphcation of the microscope to 

 anatomy in the hands of Grew, Leeuwenhoek, 

 Swammerdam, Lyonnet, Vallisnieri, Reaumur, and 

 other illustrious investigators of nature of that 

 day, disjDlayed such a complexity of organisation 

 in the lowest and minutest forms, and everywhere 

 revealed such a prodigahty of provision for their 

 multiplication by germs of one sort or another, 

 that the hypothesis of Ahiogenesis began to 

 appear not only untrue, but absurd ; and, in the 

 middle of the eighteenth century, when Needham 

 and Buffon took up the question, it was almost 

 universally discredited.^ 



But the skill of the microscope makers of the 

 eighteenth century soon reached its limit. A 

 microscope magnifying 400 diameters was a chef 

 d'ceuvre of the opticians of that day; and, at the 

 same time, by no means trustworthy. But a 

 magnifying power of 400 diameters, even when 



^ Needham, writing in 1750, says : — 



" Les naturalistes modernes s'accordent nnaninenient aetablir, 

 comme nne verite certaine, que toute plante vient de sa semence 

 specihque, tout animal d'un ceuf ou de quelque chose d'analogue 

 pieexistant dans la plante, ou dans Tanimal de meme espece qui 

 I'a produit." — Nouvdles Observations, p. 169. 



"Les naturalistes ont generalemente era que les animaux 

 microscopiques etaient engendres par des oeufs transportes dans 

 I'air, ou deposes dans des eaux donnantes par des insectes 

 volans," — Ihid. p. 176, 



