under the most excellent lenses.

Associated with the spores in the sporangium occurs the capillitium. This consists of most delicate thread-or hair-like elements, offering great variety both in form and structure. The threads composing the capillitium are not to be regarded, even when free, as cells, nor even of cellular origin; probably, as would appear from the researches of Strasburger and Harper, all forms of capillitial threads arise in connection with vacuoles in the protoplasmic mass. "Whether the thread is hollow or solid, simple or branched, free or connected with the peridium or a columella,—these are entirely secondary conditions, depending on the extent and form of the vacuoles."[6] They may occur singly or be combined into a net, they may be terete or flat, attached to the peridial wall or free, simple or adorned with bands or spires and knobs in every variety, uniform or profusely knotted and thickened at intervals, and burdened with calcic particles. In many cases, the capillitium contributes materially to the dispersal of the spores; in others, it doubtless contributes mechanically to the support of the peridial wall, and renders so far persistent the delicate sporangium. For more exact description the reader is again referred to the specific delineations which follow.

The transition from phase to phase requires, as intimated, no great length of time. Tilmadoche polycephala completed the transition from vegetative to fruiting phase in less than twelve hours.

The germination of the spores ensues closely upon their dispersal or maturity and is unique in many respects.[7] The wall of the spore is ruptured and the protoplasmic content escapes as a zoöspore indistinguishable so far from an amœba, or from the zoöspore of our chytridiaceous fungi. This amœboid zoöspore is without cell-wall, changes its outline, and moves slowly by creeping or flowing from point to point. At this stage many of the spores assume each a flagellate cilium, and so acquire power of more rapid locomotion. The zoöspores, whether ciliate or not, thus enjoy independent existence and are capable of continuing such existence for some time, assimilating, growing, and even reproducing themselves by simple fission, over and over again. This takes place, of course, only in the presence of suitable nutrient media.

Nevertheless the spores of many species germinate quickly simply in water, and a drop suspended in the form of the ordinary drop-culture on a cover-glass affords ample opportunity. In the course of time, usually not more than two or three days, the swarm spores cease their activity, lose their cilia, and come to rest, exhibiting at most nothing more than the slow amœboid movement already referred to. In the course of two or three days more, in favorable cases, the little spores begin to assemble and flow together; at first into small aggregations, then larger, until at length all have blended in one creeping protoplasmic mass to form thus once again the plasmodium, or plasmodial phase with which the round began. Small plasmodia may generally be thus obtained artificially from drop-cultures. Such, however, in the experience of the writer, are with difficulty kept alive. Hay infusions, infusions of rotten wood, etc., may sometimes for a time give excellent results.

The spores of Didymium crustaceum were sown upon a heap of leaves in autumn. An abundant display of the same species followed in the next June; but, of course, the intervening phases were not observed. The most satisfactory studies are obtained by plasmodia carefully brought in directly from the field. A plasmodium that appeared suddenly and passed to fruit on agar in a petri dish offers a valuable suggestion for further research.

With such a life-history as that thus briefly sketched, it is small wonder that the taxonomic place of the slime-moulds is a matter of uncertainty, not to say perplexity. So long as men studied the ripened fruit, the sporangia and the spores, with the marvellous capillitium, there seemed little difficulty; the myxomycetes were fungi, related to the puff-balls, and in fact to be classed in the same natural order. The synonymy of some of the more noticeable species affords a very interesting epitome of the history of scientific thought in this particular field of investigation. Thus the first described slime-mould identifiable by its description is Lycogala epidendrum (Buxbaum) Fries, the most puff-ball looking of the whole series. Ray, in 1690, called this Fungus coccineus. In 1718, Ruppinus described the same thing as Lycoperdon sanguineum; Dillenius at about the same time, as Bovista miniata; and it was not until 1729, that Micheli so far appreciated the structure of the little puff-ball as to give it a definite, independent, generic place and title, Lycogala globosum ..., etc.[8]

But Micheli's light was too strong for his generation. As Fries, one hundred years later quaintly says, ... "immortalis Micheli tam claram lucem accendit ut succesores proximi eam ne ferre quidem potuerint." Notwithstanding Micheli's clear distinctions, he was entirely disregarded, and our little Lycogala was dubbed Lycoperdon and Mucor down to the end of the century; and so it was not till 1790 that Persoon comes around to the standpoint of Micheli and writes Lycogala miniata. Fries himself, reviewing the labors of his predecessors all, grouped the slime-moulds as a sub-order of the gasteromycetes and gave expression to his view of their nature and position when he named the sub-order Myxogastres. In 1833, Link, having more prominently in mind the minuteness of most of the species collocated by Fries, and perceiving perhaps more clearly even than the great mycologist the entire independence of the group, suggested as a substitute for the sub-order Myxogastres, the order Myxomycetes, slime-moulds. Link's decision passed unchallenged for nearly thirty years. The slime-moulds were set apart by themselves; they were fungi without question and, of course, plants.

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 amœboid spores and plasmodia ally them at once to the amœba 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