In fine, it must be recognized, once for all, that organisms are not-molded on a Lamarckian basis of use, nor yet on a Darwinian basis of selected utility. Expediency, in other words, is not the sole governing principle of the organic world. Neither instinctive habitude nor the struggle for existence succeeds in forcing structural adaptation of a predictable nature. Animals with different organic structure have the same instincts, _e.g._ monkeys with, and without, prehensile tails alike dwell in trees; while animals having the same organic structure may have different instincts, _e.g._ the rabbit, which burrows, and the hare, which does not, are practically identical in anatomical structure. Again, some animals are highly specialized for a function, which other animals perform without specialized organs, as is instanced in the case of moles, which possess a special burrowing apparatus, and prairie-dogs, which burrow without a specialized apparatus. Any system of evolution, which ignores the internal or hereditary factors of organic life and strives to explain all in terms of the environmental factors, encounters an insuperable obstacle in this remorseless resistance of conflicting facts. Another flaw in the Darwinian argument from rudimentary organs is that it confounds, in many cases, _apparent_, with _real_ inutility (or absence of function). Darwin and his followers frequently argued out of their ignorance, and falsely concluded that an organ was destitute of a function, merely because _they_ had failed to discover its utility. Large numbers, accordingly, of highly serviceable organs were catalogued as vestigial or rudimentary, simply because nineteenth century science did not comprehend their indubitable utility. With the advance of present-day physiology, this list of “useless organs” is being rapidly depleted, so that the scientific days of the rudimentary organ appear to be numbered. At any rate, in arbitrarily pronouncing many important and functioning organs to be useless vestiges of a former stage in the history of the race, the Darwinians were not the friends of Science, but rather its reactionary enemies, inasmuch as they sought to discourage further investigation by their dogmatic decision that there was no function to be found. In so doing, however, they were merely exploiting the ignorance of their times in the interest of a preconceived theory, which whetted their appetite for discovering, at all costs, the presence in man of functionless organs.