the Origin of Intestinal IV^orms. 321 



these words : " Di versa scilicet diversorum viventium primor- 

 dia : pro quorum vario discrimine alii atque alii sunt genera- 

 tionis animalium modi ; qui tamen omnes in hoc uno conve- 

 niunt, quod a primordio vegetal!, tamquam e materia efficien- 

 tis virtute dotata, oriantur : difFerunt autem, quod primordium 

 hoc vel sponte et casu erumpat, vel ab alio prseexistente (tan- 

 quam fructus) proveniat. Unde ilia, sponte nascentia, Iisec a 

 parentibus genita dicuntur.'' The same observation upon Har- 

 vey's theory, Ave may add, has lately been made by Professor 

 Valentin in Burdach's Physiology, 2d edit. vol. i. p. 10. 



Sect. 4. Was much doubted after the discoveries of Profes^ 

 8or Ehrenherg concerning the Infusoria. — Within the last ten 

 years, a nev^ and most important era in the history of equi^ 

 vocal generation has arisen in Germany with the publications 

 of Professor Ehrenberg. As these are celebrated all over Eu- 

 rope, I shall point out only the most important discoveries 

 which bear on this theory. 



The first capital point in his observations is, his complete 

 confirmation of the assertions of John Hill and of O. F. 

 MiJller, that these animalcula form perfectlg distinct species^ 

 like those of other animals, and may in the same way be dis- 

 tinguished by external and internal characters. The second 

 point may be stated in as few words as the first, though it is 

 of no less importance, and the result of immense labour : " The 

 animalcula infusoria^ eve^i the smallest monades, have a very 

 complicated organization^ These unexpected discoveries, once 

 announced, gave a fatal blow to all romantic fancies about the 

 infusoria, as founded, in a great measure, upon the general 

 opinion that they were wholly destitute of organs. It is true 

 Spallanzani, as well as MUller, had previously observed certain 

 distinct parts within some of them. Corti stated that he had 

 detected a vascular system in some, and Nitzch, eyes in others ; 

 but these assertions were but little attended to. At length, 

 Dutrochet supplied a description of the very complete organi- 

 zation in some of the larger infusoria — the Rotifera, whilst 

 others still remained, in the last edition of Cuvier's Regne Ani- 

 mal (1829), as '' infusoires homogcnes'^ . Thus the imagina- 

 tion had full scope for further speculation ; and if the discovery 

 of a complete organization in the animalcula infusoria has 

 given a fatal blow to the tlieory of a spontaneous generation^ 



