the same leaves, sometimes from the same patches, and, as it would appear, from the same mycelium. The great difference in the two species lies in the fructification. In the _Penicillium_, the spores are naked, and in moniliform threads; whilst in _Mucor_ the spores are enclosed within globose membraneous heads or sporangia. Scarcely can we doubt that the _Mucor_ alluded to above, found thus intermixed, under peculiar circumstances, with _Penicillium roseum_, is no other than the higher and more complete form of that species, and that the _Penicillium_ is only its conidiiferous state. The presumption in this case is strong, and not so open to suspicion as it would be did not analogy render it so extremely probable that such is the case, apart from the fact of both forms springing from the same mass of mycelium. In such minute and delicate structures it is very difficult to manipulate the specimens so as to arrive at positive evidence. If a filament of mycelium could be isolated successfully, and a fertile thread, bearing the fruit of each form, could be traced from the same individual mycelium thread, the evidence would be conclusive. In default of such conclusive evidence, we are compelled to rest with assumption until further researches enable us to record the assumption as fact.[k] Apropos of this very connection of _Penicillium_ with _Mucor_, a similar suspicion attaches to an instance noted by a wholly disinterested observer to this effect. "On a preparation preserved in a moist chamber, on the third day a white speck was seen on the surface, consisting of innumerable 'yeast' cells, with some filaments, branching in all directions. On the fourth day tufts of _Penicillium_, had developed two varieties--_P. glaucum_ and _P. viride_. This continued until the ninth day, when a few of the filaments springing up in the midst of the _Penicillium_ were tipped with a dewdrop-like dilatation, excessively delicate--a mere distended pellicle. In some cases they seemed to be derived from the same filament as others bearing the ordinary branching spores of _Penicillium_, but of this I could not be positive. This kind of fructification increased rapidly, and on the fourteenth day spores had undoubtedly developed within the pellicle, just as had been observed in a previous cultivation, precisely similar revolving movements being also manifested."[l] Although we have here another instance of _Mucor_ and _Penicillium_ growing in contact, the evidence is insufficient to warrant more than a suspicion of their identity, inasmuch as the equally minute spores of _Mucor_ and _Penicillium_ might have mingled, and each producing its kind, no relationship whatever have existed between them, except their development from the same matrix.