Unfortunately, that is downfall of the Aigle boot - the rubber breaks down. You can goop, tape etc, but you are just prolonging the inevitable. If you get a new pair, keep them well coated with a UV protector (armor all, seal saver etc) and when not in use, throw them in a sealed bag and out of the sun.
In consent to 49208. I only have to add: sometimes "vulcanization" helps. The Aigles are made out of rubber. So, I guess, (cold way)vulcanization is possible. Ask f.e. a shoemaker or at a local tyre shop for the costs. The work usualy not really is durable forever and the visual result of vulcanization (in my opinion) looks "uncool", but often it's cheap. Butto the other side: new replica-Aigles of "Dry Fashion" (sometimes offered at "ebay & Co.") are cheap, too.