1 INTKODUCTION. 



spread out and cover up any object left oii 

 the surface. I was thus led to conchide that 

 all the vegetable mould over the whole coun- 

 try has passed many times through, and will 

 again pass many times through, the intestinal 

 canals of worms. Hence tlie term " animal 

 mould " would be in some respects more 

 appropriate than that commonly used of 

 *' vegetable mould." 



Ten years after the publication of my paper, 

 M. D' Archiac, evidently influenced by the doc- 

 trines of Elie de Beaumont, wrote about my 

 "singuliere theorie," and objected that it could 

 apply only to "les prairies basses et humides;" 

 and that "les terres laboure'es, les hois, les 

 prairies elevees, n'apportent aucune preuve 

 a I'appui de cette maniere de voir." * But M. 

 D'Archiac must have thus argued from inner 

 consciousness and not from observation, for 

 worms abound to an extraordinary degree in 

 kitchen gardens where the soil is continually 

 worked, though in such loose soil they generally 

 deposit their castings in any open cavities or 

 within their old burrows instead of on the 

 surface. Yon Hensen estimates that there are 



* • Histoirc des progifes de la Geologic,' tom. i. 18i7, p. 224, 



