We are not as yet entitled to conclude definitely against the possible inheritance of acquired characters. Consequently, we are not as yet entitled to assume that climatic characters--i. e. characters acquired by converse with a new environment, continued, say, since the last glacial period--can never have become congenital characters. But, if they ever have become congenital characters, they will have become, at all events as a general rule, congenital characters that are useless; for it is conceded that, _quâ_ climatic characters, they have not been due to natural selection. Doubtless the followers of Weismann will repudiate this line of argument, if not as entirely worthless, at all events as too questionable to be of much practical worth. But even to the followers of Weismann it may be pointed out, that the Wallacean doctrine of the origin of all specific characters by means of natural selection was propounded many years before either Galton or Weismann had questioned the transmission of acquired characters. However. I allow that this line of argument has now become--for the time being at all events--a dubious line, and will therefore at once pass on to the second line, which is not open to doubt from any quarter. Whether or not we accept Weismann's views, it will here be convenient to employ his terminology, since this will serve to convey the somewhat important distinctions which it is now my object to express. In the foregoing paragraphs, under heading (A), we have seen that there must be "literally numberless forms" which have been ranked as true species, whose diagnostic characters are nevertheless not congenital. In the case of plants especially, we know that there must be large numbers of named species which do not conform to the criterion of Heredity, although we do not know which species they are. For present purposes, however, it is enough for us to know that there are many such named species, where some change of environment has acted directly and similarly on all the individual "somas" exposed to it, without affecting their "germ-plasms," or the material bases of their hereditary qualities. For named species of this kind we may employ the term _somatogenetic species_. But now, if there are any cases where a change of environment does act on the germ-plasms exposed to it, the result would be what we may call _blastogenetic species_--i.e. species which conform to the criterion of Heredity, and would therefore be ranked by all naturalists as "true species." It would not signify in such a case whether the changed conditions of life first affected the soma, and then, through changed nutrition, the germ-plasm; or whether from the first it directly affected the germ-plasm itself. For in either case the result would be a "species," which would continue to reproduce its peculiar features by heredity.