6 INTRODUCTION. 



In the year 1869, Mr. Fish* rejected my 

 conclusions with respect to the part which 

 worms have played in the formation of veget- 

 able mould, merely on account of their assumed 

 incapacity to do so much work. He remarks 

 that " considering their weakness and their 

 ' size, the work they are represented to 

 " have accomplished is stupendous.'* Here we 

 have an instance of that inability to sum 

 up the effects of a continually recurrent 

 cause, which has often retarded the progress 

 of science, as formerly in the case of geology, 

 and more recently in that of the principle 

 of evolution. 



Although these several objections seemed 

 to me to have no weight, yet I resolved to 

 make more observations of the same kind as 

 those published, and to attack the problem on 

 another side ; namely, to weigh all the cast- 

 ings thrown up within a given time in a 

 measured space, instead of ascertaining the 

 rate at which objects left on the surface were 

 buried by worms. But some of my observa- 

 tions have been rendered almost superfluous 

 by an admirable paper by Yon Hen sen, 



* ' Gardeners' Chronicle,' April 17, 1869, p. 418. 



