320 LECTURE VII. 



stincts which cause it to protrude them 

 one bj one out of its cavity ? * How cu- 

 rious also is the mode by which the con- 

 tinuance of the species of the oestrum equi 

 is effected ? Surely it is wonderful that 

 this fly, as if endowed with intelligence, or 

 instructed by experience, should never de- 

 posit its eggs, but in those parts of the horse 

 to which that animal can apply its mouth, 

 so that they may be swallowed. By this 

 means the larvae are provided with a warm 

 lodging and plenty of food during the win- 

 ter season, and are not expelled till spring, 

 in order to undergo their metamorphosis 

 into perfect flies. I must not proceed fur- 

 ther in this endless subject, the full investi- 

 gation of which has convinced the most 

 intelligent of mankind, that the order of 

 Nature is the result neither of necessity 

 nor chance. 



Every part seems perfect in its design, 

 and calculated for the good of the indi- 



* Cuckoos however have been known to hatch their 



own eggs. 



