316 Dr Eschricht's Inquiries concerning 



century, such unexpected facts were ascertained respecting 

 them as could scarcely be explained otherwise than by admit- 

 ting their spontaneous origin ; and about half a century later 

 (1745-1764), the neglected hypothesis of the ancients found, 

 nearly at the same time, several eminent defenders, namely, 

 Needham in England, Buffon in France, and Wrisberg in Ger- 

 many. The ingenious speculations of these natural philoso- 

 phers could scarcely be overpowered by Spallanzani and Tere- 

 chowsky ; on the contrary, they rather appeared confirmed by 

 the experiments of Monti, Ingenhouse, Priestley, and others. 

 Succeeding inquirers into the history of the infusoria, were ge- 

 nerally imbued with theoretical views highly fg-vourable to the 

 spontaneous origin of living bodies. They regarded the in- 

 stances established by John Hill, in his " History of Ani- 

 mals," and by Otho Frederic Miiller, in his celebrated " Ani- 

 malcula infusoria," more as abstract types originating out of 

 a boundless variety, than as real distinct species like those of 

 animals in general ; and considered the infusoria generally as 

 living particles without any certain structure or form. It was 

 alleged that one of the larger infusoria might be changed into 

 smaller ones, wholly differing both in shape and habits. The 

 character of these animalcules was said to depend chiefly, if 

 not entirely, upon external influences ; quite the reverse of 

 what happens in the case of organized bodies, whose charac- 

 teristic it is to be developed in conformity with a certain rule, 

 even under a great variety of external influences. " If we take 

 a greater or less quantity of water," it was observed, "stronger 

 or weaker light, higher or lower temperature, we shall always 

 obtain different animalcules from the same organic substances : 

 again, if these substances be differently treated before they 

 are employed in making the infusions, if they be raw or boiled, 

 pulverized or entire, dried or fresh, &c. the procreated being 

 will be different in kind." Hence the Miillerian forms were 

 not regarded as characters of constant species, but merely as 

 very inconstant types of no precise import in science. 



The learned and ingenious G. R. Treviranus of Bremen (in 

 his Biologic, 2d and 5th volume, 1803-5) proposed the theory 

 of an indelible but infinite variety of all organic matter. Pro- 

 vided with an internal occult life, it could assume new forms, 



