Lamarck's Letter to Darwin

Dear Monsieur Darwin,
I was happily sipping my afternoon tea with the Prime Minister of France, when a fellow scientist burst in through the double doors and so conversationally mentioned that you have discredited my ingenious theory of evolution. Now, if I wasn’t with someone with high authority, I would’ve given my fellow scientist a good beating for spreading and believing in such rubbish. Of course, I laughed it off and reassured the Prime Minister that I was still a very important person, and it is not possible for my theory to be disproved. My innovational theory is backed up with substantial evidence from years of studying the fossils of organisms that would surely laugh at your ridiculous idea.
I do agree with you – grudgingly – that the environment is changing gradually and leisurely, and animals will have to adapt to the changes to be more suited to its surroundings and survive, but that is the only thing we agree on. I believe that organisms adapt, and change their physical structure at will as time passes by, and they pass on the traits to their offspring. When they use one organ or body part more, that organ or body part will be more developed. The same thing happens when a body part is not always used, an organism will, over time, lose that body part.
Take the Giraffe for example, the fossils that I studied suggests that the long-necked giraffes that we see today had ancestors that had short necks and,   over time, their necks stretched because they kept on stretching them to reach the leaves on top of the trees.   A “nervous fluid” runs up to the neck of the giraffe and makes it grow longer. The physical attributes and the improved organs that they have gained over their life time, they passed on to their offspring. The process of continually stretching their neck would cause it to become longer over several generations until they become he giraffes that we see today.
I do hope that this will bring some sense into your head, Monsieur Darwin....