“In some cases,” this author writes, “and under favourable circumstances, I have been able to see the ferment produce filaments, both small specimens that could be examined immediately under the microscope, and also large specimens, and I have recognized, amongst other varieties, _penicillium glaucum_, _ascophora mucedo_, _ascophora elegans_, and _periconia hyalina_, sometimes isolated, sometimes intermixed. This result is most easily to be obtained by the following method:—Pour a small quantity of water into a test-tube, which should then be placed slantingly: introduce some fresh yeast into the middle part of the tube, and close the tube with a wad of cotton, to prevent the entrance of exterior particles of dust. In this vapour-filled receptacle we shall sometimes see flakes develop. It seems that Messrs. Berkeley and G. H. Hoffmann have also obtained _penicillium_ from ferment, by a similar process.”[57] Why, however, should it not be admitted that _penicillium_ found under such conditions may be derived from spores of that growth, adhering to the sides of the tube before it is closed with the wad, or mixed with the yeast that is put into the tube? The facts alleged during the last few years by M. Bail, who persists in his views, in spite of their apparently greater exactness, are also far from being satisfactory.[58] M. Trécul, who is almost the only one in France, besides Messrs. Ch. Robin and Fremy, to participate in these errors, does not confine himself to affirming the change of the spores of _penicillium_ into yeast, and _vice versâ_; his system is a far more extensive one. “According to my observations,” he says, “there would be the following series of changes; albuminous matter changed into _bacteria_, or directly into alcoholic ferment, or into _mycoderma_; _bacteria_ into lactic ferment, there becoming immoveable; lactic ferment into alcoholic ferment; alcoholic ferment into _mycoderma cerevisiæ_; finally, _mycoderma cerevisiæ_ into _penicillium_.[59]” M. Trécul does not stop here. He goes on to explain the principal of these changes, as though his testimony were quite beyond refutation: