PART A: Based on the readings in Ruse, was there a “Darwinian Revolution,” and

 PART A: Based on the readings in Ruse, was there a “Darwinian Revolution,” and how have scholars debated this idea since he first published his book by that title in 1979? 
Part B:  Why did Darwin wait so long to publish On the Origin of Species?
Explain your answer in 250-400 words.
References:
  Bertoloni, M. D. E. I., Dorn, H., & McClellan, J. E. I. (2006). Science and technology in world history: An introduction. Johns Hopkins University Press. 
 Ruse, M. (2008). Charles darwin. John Wiley & Sons, Incorporated. Pages: x-x11, 1-20, 21-53, 287-307