The often quoted example of Lamarkism is the elongation of a giraffe's neck.
Yes, because in the age old story, our giraffe wanted so much to reach those tasty leaves up high, that he streeeeetcheeeeed his neck so he could reach them. And low and behold he now had a long neck. Which by Lamarkism he passed onto all of his descendenrts. But by evolution, of course, he did not. He was just one long necked giraffe, and all his descendents had the same short necks as he had at birth.
You can only pass on the genes you inherited at conception, which may be modified by later germline mutations.
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