with the result that all the changes produced in each set of plants were similar--just as in the cases where similarly "climatic" modifications are not hereditary, and therefore unquestionably due to changed conditions acting on roots, stems, leaves, or flowers, as the case may be. On the other hand, it is not thus intelligible that during the short time of germination the changed conditions should effect a re-shuffling (or any other modification) of the "germ-plasm" in the seeds--and this in such a manner that the effect on the residual germ-plasm reserved for future generations is precisely similar to that produced on the somatic tissues of the developing embryo. In the second place, as we have seen, in some of the foregoing cases the changes were produced months--and even years--before the seeds of the first germination were formed. Therefore the hereditary effect, if subsequent to the period of embryonic germination, must have been produced on germ-plasm as this occurs diffused through the somatic tissues. But, if so, we shall have to suppose that such germ-plasm is afterwards gathered in the seeds when these are subsequently formed. This supposition, however, would be radically opposed to Weismann's theory of heredity: nor do I know of any other theory with which it would be reconcilable, save such as entertain the possibility of the Lamarckian factors. Lastly, in the third place, I deem the following considerations of the highest importance:-- "As other instances in which peculiar structures are now hereditary may be mentioned aquatic plants and those producing subterraneous stems. Whether they be dicotyledons or monocotyledons, there is a fundamental agreement in the anatomy of the roots and stem of aquatic plants, and, in many cases, of the leaves as well. Such has hitherto been attributed to the aquatic habit. The inference or deduction was, of course, based upon innumerable coincidences; the water being supposed to be the direct cause of the degenerate structures, which are hereditary and characteristic of such plants in the wild state. M. Costantin has, however, verified this deduction, by making terrestrial and aerial stems to grow underground and in water: the structures _at once_ began to assume the subterranean or aquatic type, as the case might be; and, conversely, aquatic plants made to grow upon land _at once_ began to assume the terrestrial type of structure, while analogous results followed changes from a subterranean to an aerial position, and _vice versa_."