If the hypha is the morphological test of a fungus, then it is plain that the slime-moulds are not fungi. No myxomycete has hyphæ, nor indeed anything at all of the kind. Nevertheless, there are certain parasitic fungi, _Chytridiaceae_ for example, whose relationships plainly entitle them to a place among the hyphate forms that have no hyphæ whatever in the entire round of their life-history. These are, however, exceptional cases and really do not bear very closely on the question at issue.
Physiologically, the fungi are incapable of independent existence, being destitute of chlorophyl. In this respect the slime-moulds are like the fungi; they are nearly all saprophytes and absolutely destitute of chlorophyl. Unfortunately this physiological character is identically that one which the fungi share with the whole animal world, so that the startling inquiry instantly rises, are the slime-moulds plants at all? Are they not animals? Do not their amoeboid spores and plasmodia ally them at once to the amoeba and his congeners, to all the monad, rhizopodal world? This is the position suggested by DeBary in 1858, and adopted since by many distinguished authorities, among whom may be mentioned Saville Kent, of England, and Dr. William Zopf, of Germany, in _Die Pilzthiere_, 1885. Rostafinski was a pupil of DeBary's. However, his volume on the slime-moulds was written after leaving the laboratory; and no doubt with the suggestion of his master still before his mind, he adopts the title Mycetozoa, as indicating a closer relationship with the animal world, but our leading authority really has little to say in regard to the matter.[9]
Dr. Schroeter, a recent writer on the subject, after showing the probable connection between the phycochromaceous Algae and the simplest colorless forms, namely, the _Schizomycetes_, goes on to remark: "At the same point where the Schizomycetous series take rise, there begin certain other lines of development among the most diminutive protoplasmic masses.... Through the amoebæ one of these lines gives rise on the one hand to rhizopods and sponges in the animal kingdom, on the other to the _Myxomycetes_ among the fungi." This ranges the Myxomycetes, in origin at least, near the _Schizomycetes_.