“the existing knowledge in the particular field, the extent and content of the prior art, the maturity of the science or technology, [and] the predictability of the aspect at issue.” Id. at 1359. The law must be applied to each invention at the time it enters the patent process, for each patented advance has a novel relationship with the state of the art from which it emerges. Thus, we do not try here to predict and adjudicate all the factual scenarios to which the written description requirement could be applied. Nor do we set out any bright-line rules governing, for example, the number of species that must be disclosed to describe a genus claim, as this number necessarily changes with each invention, and it changes with progress in a field. Compare Eli Lilly, 119 F.3d at 1567 (<HOLDING>), with In re Wallach, 378 F.3d 1330, 1334
holding that letter stating an annual salary did not embody the terms of any agreement between the parties as it did not specify a beginning date duration of time and did not require acceptance signatures holding an amino acid sequence did not describe the dna sequence encoding it holding that it may not holding that it is not holding that the trial court did not err when it refused to find an implied easement by necessity because the plaintiff did not demonstrate necessity