In several instances the fermentation in wine juice was started by the addition of brewers' yeast.

The juice was prepared from foreign red grapes, and the percentage of glucose was made up in one instance to 36 and in another to 31 per cent. To each sample, which consisted of about two quarts, 250 grains of brewers' pressed yeast were added, and the fermentation was conducted in a chamber at a temperature of 70° Fahr. On the third day a small quantity of fresh husks of English hot-house grapes with pulpy matter attached was added to each sample, to ensure, as was thought, sufficient fermentative power.

At the end of fourteen days the samples contained respectively 13.23 and 15.91 per cent. of alcohol, and at the end of a month the percentages were 13.76 and 15 96, being only an increase during the interval of 53 in the former case, and 05 in the latter, so that it was obvious the fermentation in both was completely suspended.

The wine was then carefully drawn off, and a sugar solution. was added to each residue, and the flasks were replaced in the fermenting chamber. In a few days a brisk fermentation commenced in both samples, and at the end of a week they contained 7 and 6.5 per cent. of alcohol respectively, thereby showing that the fermentative power was not exhausted, and that the stoppage of the fermentation was due to some other cause.

Now it must be observed that the fermentation had proceeded to a considerable extent before the yeast cells natural to the grape juice had time to develop, and there is no doubt that the alcohol previously generated seriously affected their growth and propagation.

An experiment which was made on another sample will perhaps tend to explain this.

A wine juice made up to 36 per cent. of glucose, and from which the greater part of the husks and pulpy matter had been separated, ceased to ferment when the alcohol had reached 15.97 per cent. With a view of trying to push the fermentation further, a quantity of fresh husks and pulpy matter was added, which had the effect of reducing the proportion of alcohol present to 13 93 per cent. The sample was then successively tried in a chamber kept at a temperature of 68° and 80° Fahr., but no further fermentation could be induced, a result which would appear to indicate that to obtain a good and an exhaustive fermentation the cells require to develop naturally in the juice, and become gradually acclimatized to the successive changes of conditions produced during the progress of the fermentation.

Effect of Change of Soil.-A few experiments have been made

to ascertain the influence of change of soil upon the development of the yeast plant.

To a solution containing 32 24 per cent. of glucose some albuegg and a small quantity of healthy wine ferment were added, and the sample was placed in a chamber maintained at a temperature of about 67° Fahr.

The wine yeast cells remained bright and healthy, but did not appear to possess much activity; in the course of seven or eight days albumen cells were developed, and there was an apparent action going on in the liquid.

At the expiration of nineteen days the sample was examined for alcohol, and it was found to contain only 71 per cent., and at the end of a month it was again examined and found to contain 92 per cent. and one-tenth per cent. of acid.

It was obvious from this result that the soil was unsuited for the growth and propagation of the wine yeast cells. The sample was now diluted by the addition of water until the percentage of glucose was reduced to 18 per cent. This change of condition, however, had little influence in promoting the action of the cells, and the percentage of alcohol at no time afterwards was found to exceed 1·04 per cent.

At the end of several weeks a new form of fungoid growth was found to have been developed in the liquid and a great mass of fresh cells produced, whose action appeared to have completely superseded the alcoholic ferment, and when the sample was next examined it was found to contain no alcohol whatever, but 2.80 per cent. of acid.

Two malt extracts were prepared, and the glucose present was made up in each case to about 30 per cent. To one sample wine ferment was added, and to the other malt ferment. The experiments were conducted, so far as was practicable, under the like conditions; but the results were somewhat different, the proportion of alcohol produced in the sample to which the malt ferment had been added having exceeded the quantity produced in the other; and it may be added that the spirits produced in the samples were perceptibly different in flavour.

Although this experiment is not regarded as conclusive, still it is worth recording, as the result tends to the same conclusion as that indicated by the results obtained in some of the other experiments, in showing that the different ferments have their favourite soils, and that they flourish best in those natural to them.

The results of the experiments would probably bear a more general conclusion in indicating a comparative inactivity of fungoid spores, unless when they meet with a soil that is favourable to their growth and development.

This paper, it will be noticed, extends over a wide field, and there are many points which require further elucidation. With this view additional experiments are being made, and I hope shortly to be able to go more fully into some of the subjects that are here but lightly touched upon.

EXPLANATION OF PLATE LV.

FIG. 1.-Cells from egg albumen in sugar solution.

2.-Cells from gluten in sugar solution.

3 and 4.-Cells and mycelium from flour and malt albumen in sugar solutions. 5.-Yeast cells developing in mucilage in barley meal extract.

6.-Mould, &c., from malt extract in sugar solution.

7.-Mould from lemon juice in sugar solution.

8.-Mycelium and cells from pus in sugar solution.

9.-Exhausted cells from wort ferment.

II.-The Origin of the Colouring Matter in Mr. Sheppard's Dichroic Fluid. By E. RAY LANKESTER, B.A., F.R.M.S.

(Read before the ROYAL MICROSCOPICAL SOCIETY, June 8, 1870.) MR. PRESIDENT,—Since you have lately twice publicly alluded to the views I expressed on the above matter in 1867, and have declared that the recent observations of my friend Mr. Sorby have entirely "disestablished" those views, I beg to forward you these few lines relative to the matter, and to assure you that, so far from being in the position of the Irish Church, the opinion which I held is entirely confirmed by what has since transpired.

6

Mr. Sheppard's paper, published in the Quarterly Journal of Microscopical Science, 1867, p. 64, was entitled "On an Example of the Production of a Colour possessing remarkable Properties by the Action of Monads (or some other microscopic organism) upon Organized. Substances," and he distinctly advocates therein (as did you also, I believe) the view that the dichroic fluid was due to the conversion of albumen artificially added or naturally present by the working of some monads or other. He refers to Pasteur's observation of the action of monads in changing the colour of certain bodies, and no one can deny for a moment that this was his and your view of the origin of the colour.

It was this method of looking at the matter which I declared to be "unnecessarily conjuring up a mystery," to which opinion I still most strongly adhere. At the same time I acknowledged in my note in the Quarterly Journal of Microscopical Science,' 1867, p. 284, the great interest of Mr. Sheppard's observations, and I am glad to be able again to say that we are indebted to him in

England for drawing so many persons' attention to the subject. In my letter, which you have considered to be disestablished by Mr. Sorby's paper, I express the opinion that Mr. Sheppard's coloured fluid probably owes its colour to Cohn's Phycocyan, or a closelyallied body, and that opinion is shared by Mr. Sorby and everyone else with whom I have conversed who has looked into the question, and I am unable to see in what respect Mr. Sorby's observations confute my views, since they are almost identical with his own. Mr. Sheppard declared that his coloured fluid could not have resulted from the algae which were present, most emphatically. Now I imagine there is no one who will not admit that it does result from decaying algae (the colour existing in living algæ at first), which I stated in the letter supposed to be disestablished, and which Mr. Sorby fully endorses in his paper, speaking, as he does, of the confervoid growth "decomposed with water" and "decomposed with albumen.'

The fact is, Sir, that, word for word, I am prepared to repeat the letter published in 1867, and beg your readers to turn to it in order to spare your space. They will find that, so far from being disestablished, the view which I expressed-which was the simple, straightforward one is the view which everybody takes-probably Mr. Sheppard himself—at the present time.

There are two important facts indicated in Mr. Sorby's paper which have nothing whatever to do with the above matter, but which I will here mention. He endeavours to show that from Mr. Sheppard's two-banded fluorescent fluid—which I am inclined to consider identical with Cohn's Phycocyan, but which Mr. Sorby, not having seen Cohn's paper, does not feel sure about a singlebanded blue and a single-banded red fluid may be obtained. He succeeds in obtaining the red fluid from the two-banded fluid of Mr. Sheppard by the action of absolute alcohol. The single-banded blue fluid he has obtained from fresh specimens of confervoid growth "decomposed with water." The separation of these two colours is important, but it does not in the least affect their relation to the Phycocyan of Cohn, for the spectrum of Phycocyan as figured by Cohn is two-banded (except a very faint line at 9), and agrees with that of Mr. Sheppard's fluid, if we make allowance for strength of solution and difference of spectroscopes. The second point which Mr. Sorby makes out is an action of albumen in promoting the formation of the second constituent of Mr. Sheppard's solution. This very different from the action which Mr. Sheppard supposed he had made out, namely, that the albumen was converted into a colouring matter by monads. Mr. Sorby seems to think that the albumen really takes part in promoting a chemical change of the cell contents or of the colouring matter of the Oscillariæ. If it does, its action is merely "catalytic," as chemists say; but I believe that it

is

Journal,

simply causes a more rapid solution to be obtained by its affinity for the colouring matter in the still living algæ, or by starting the decomposition of the Oscillaria favours the solution of this part of its pigment. Any such action of albumen would be very different from Mr. Sheppard's monad-mystery.

It is worth noting that Cohn speaks of a red modification of his Phycocyan (which is usually blue in solution with carmine fluorescence), not to be confounded with his Phycoerythrin, which gives an exact parallel to Mr. Sorby's observation of a blue and a red condition of the fluid from such confervoid growths as Mr. Sheppard's.

The discussion about the origin of this colour is really almost ludicrous, and very nearly as devoid of justification as would be a discussion as to the origin of the yellow colour when saffron is put into water. The drawings of Mr. Sheppard's confervoid growth which you were so kind as to send for my inspection, prove it to be one of the true Oscillariæ as defined by Kutzing. Some of a growth which Mr. Sorby has had the great kindness to send me from Derbyshire belongs to the same species. Now it is an established fact that these algæ, as well as certain lichens and fungi, give colouring matters soluble in water after the death of the plant, and often fluorescent. It is a serious obstacle to the progress of knowledge when the work of previous observers is ignored, and wild speculation is used instead of the comparison of fact with fact. The paper of Cohn in Max Schultze's Archiv,' 1867, Part I., must be looked at by those who wish to discuss this question; also that of Dr. Askenasy in the 'Botanische Zeitung,' July 1867, which is a most interesting memoir, giving intensity diagrams of the spectra of-1, a colour from Oscillariæ, allied to or perhaps the same as Mr. Sheppard's, and as Cohn's Phycocyan, though there is discrepancy in the figures given by the three authors of the spectrum, which is easily accounted for; 2, of a similar colour from the lichen Peltigera canina; 3, of another similar colour from Collema. The colouring matter known as Cudbear, obtained from a lichen, may be also studied in comparison with the colour from Oscillariæ.

It is a mistake to suppose that the mats of Oscillarian growth are dead because they have such a powerful and unpleasant smell. It is not until they are dead that the cells of the plant allow the colouring matter to pass into the water, but it is easily to be recognized in the living fronds. Its presence in the water is the result of the decay of the algae, but it is formed in the living plant.

I am able to give a very complete answer to the theories as to the formation of the colour outside the plant and after its death (which are, indeed, inconsistent with all analogy) by the study of some of the growth-identical with Mr. Sheppard's-for which I am indebted to Mr. Sorby's kindness. The two bands described