SUMMARY. 81 



considered, intricate mathematical problems arise 

 which, are probably more complicated than ques- 

 tions in astronomy. The possible number of 

 combinations of movements is finite, as is easily 

 illustrated. It appears probable that a very direct 

 analogy may be made between series of movements, 

 and series of acts of growth, and that similar laws 

 may govern both. 



