How can I get a reference to a method?

Is it possible in Ruby to get a reference to methods of an object ( I would like to know if this can be done without procs/lambdas ) , for example , consider the following code :

class X
  def initialize
    @map = {}
    setup_map
  end

  private
  def setup_map
    # @map["a"] = get reference to a method
    # @map["b"] = get reference to b method
    # @map["c"] = get referebce to c method
  end

  public
  def call(a)
    @map["a"](a) if a > 10
    @map["b"](a) if a > 20
    @map["c"](a) if a > 30
  end

  def a(arg)
     puts "a was called with #{arg}"
  end

  def b(arg)
     puts "b was called with #{arg}"
  end

  def c(arg)
    puts "c was called with #{arg}"
  end
end

Is it possible to do such thing ? I would like to avoid procs/lambdas because I want to be able to change the behaviour of A,B,C by subclassing .