Fischel also tried the effect of removing a part of the upper edge of the iris at the time when the lens was extirpated, in order to see if, in the absence of this part, the lens would develop from other parts of the uninjured margin of the iris. He found that the new lens still comes from the upper edge of the iris from the part left after the operation and not from the intact edge in other parts. This seemed to show that an injury to the iris is in itself a stimulus that starts the formation of a lens. This conclusion is made probable by the results of other experiments in which the iris was stuck at several points, when new lenses began to develop at several of these regions of injury. In some cases Fischel found that two or more lenses began to develop when the iris had not been intentionally injured; but it is not improbable that some sort of injury may have been effected when the lens was removed. Fischel, as has been said, removed extensive portions of the upper part of the iris and found that a new lens could be formed at the cut-edge, even in the region of the _pars ciliaris_; and, even after the removal of the entire upper part of the iris, lens-like structures may appear in the inner or retinal layer of the remaining region. If instead of removing the lens it is displaced by pressing on the cornea until the lens leaves its normal position and comes to lie in the vitreous humor, a new lens develops from the edge of the iris, as though the old lens had been entirely removed from the eye, but in the experiments in which this was done the new lens was not well developed. The result shows that it is not necessary that the old lens be removed from the eye in order to induce the regeneration of a new one, but only that the lens lose its normal position in the eye. In regard to the stimulus that determines the development of the lens, Fischel agrees with Wolff that gravity has a share in producing the result. The absence of the old lens from its normal position, as well as the wrinkling of the cornea, may also enter in as factors. Fischel takes issue with Wolff as to the interpretation of the result as an adaptation, and states that “the organism always responds to a change of relation in only one way, whose direction is already determined by internal structural relations, without regard to whether the result is adaptive or not. The response follows each stimulus in a way determined by the limited possibilities of the cells. With such a uniformity in the reaction, the idea of a fundamental adaptability cannot be connected, since the reaction that appears to us to be adaptive in a series of complicated changes may be non-adaptive in another series.”