On the other hand, I am not unprepared with an array of facts which seem to me capable not only of neutralizing the force of the preceding argument, but of making it appear, most likely, that some other influence than that of the experimenter’s mind is often in operation in bringing about these results; an influence sufficiently curious, as I think, to justify me in continuing this investigation and the present letter. I beg the reader’s candid construction of the following statements. If, when trying the odometer, I have caused it, by conceiving a different motion, to change its path and move in a _wrong_ direction, I now endeavour to divert my mind from considering its motion at all, the odometer invariably resumes its previous _right_ movement. It is, indeed, difficult to observe a strict mental neutrality in this instance. For the odometer moves imperfectly and uncertainly, unless I frequently look at its performance. Or, as I interpret the fact, unless I keep my attention fixed to a certain extent on what I am doing, my hand loses its steadiness, and communicates all sorts of distracting impulses to the pendulum. And the uncertainty hence arising admits, it appears to me, of being obviated by the comparison of numerous careful repetitions of the experiments. Many of the motions which I at first thought were genuine Od-results, I afterwards found out I had been mistaken in. And the correction of these errors was mostly due to frequent and careful repetitions of the experiments, unattended by an expectation of finding the results reversed or otherwise modified, and instituted simply to secure their genuineness and certainty. Then there was one result which at one time I confidently anticipated; but it never came up. I had found the ring make gyrations in the direction of those of the hands of a watch, when held over the small end of a living unincubated egg. Opposite gyrations were obtained over the big end. I thought this might have to do with the sex of the embryo. And I tried, accordingly, a dozen eggs, expecting that in some the direction of the gyrations at the two ends would be reversed. But this event never occurred, much as I laid myself out for it. If my fancy could have decided the matter in spite of my care to prevent its interference, I am clear that for a time, at least, I should have obtained in these experiments upon the egg a double set of results. I was much delighted two months later at coming upon the explanation of the question, why gyration like that of the hands of a watch is manifested at the little end of the egg. I had known from nearly the first that this direction of the rotatory Od-motion is manifested when the pendulum is swung over the right side of the human body. Then I fell upon an old physiological reminiscence, (and found a drawing of the fact in my outlines of Physiology,) that the embryo chick lies in the egg transversely upon its face, with its right side towards the little end.