Some reference must be made here to observations of Prof. Bateson in his work on variation. In the first place he makes a most valuable statement that “_the environment as the directing cause is essential to Lamarck’s theory and as the limiting cause is essential to the doctrine of Natural Selection_”[36] (which I venture to place in italics on account of its importance to all who seek the pathway of organic evolution) and points out also that “diversity of environment is thus the measure of diversity of specific form. Here then we meet the difficulty that diverse environments often shade into each other insensibly and form a continuous series.”[37] This is clearly true and important to the subjects he is discussing. But in regard to the conception with which I am here concerned, that of _total experience_ of organisms, it must be remembered that there is no such thing as an environment apart from the living beings that it environs, and that from this point of view there is no such thing in the world of nature as a continuous environment. The environment of two amœbæ living under a cover-glass is, for them, far from continuous. In their infinitesimal existence the exact position they occupy in the environing drop of fluid, in which the proportion of their humble fare at one side of the cover-glass is not the same as that on the opposite side, renders their environments discontinuous, or different from that of another amœba occupying a position and “environment” which _we_ should consider identical. And this consideration applies to the other few “tropisms” which enter into their little lives. This statement may be difficult to prove, but it is a necessity of thought. An illustration may assist one in visualizing such discontinuity. A fly is seen crawling at its own pace up one of the great pillars of St. Paul’s Cathedral. It comes to one of the thin layers of cement worn down with age and so delicate that a man can just see it in a good light. The fly pauses, and passes into what is for it a chasm, with as much relative deliberation as the man would show in passing across a deep railway cutting. The number of pictures that could be made of cases corresponding to that of the amœba is incalculable. A few will suffice. Two plants of the common nettle are growing on the south side of a ditch in a lane, one rooted a foot higher than the other. The upper one receives throughout its life from wind and sun stimuli slightly different from those received by the lower, and from the soil slightly less moisture. These again receive stimuli very different from another pair on the northern side of the lane. Again in windy weather a clump of sycamores facing the south-west in England, and situated on the ridge of an eminence, will receive very different stimuli from a similar clump on the north-eastern slope of this eminence, and will demonstrate the fact, as to force of wind, by a marked slope to the North East. Even in either of the clumps the