HARDWICKE'S SCIENCE-GOSSIP, 



II 



which, moreover, generally indicate, according to our 

 theory, the actual steps by which the instinct has been 

 acquired, inasmuch as we suppose allied instincts to 

 have branched off at different stages of descent from 

 a common ancestor, and therefore to have retained, 

 more or less unaltered, the instincts of the several 

 lineal ancestral forms of any one species ; bearing all 

 this in mind, together with the certainty that instincts 

 are as important to an animal as their generally 

 correlated structures, and that in the struggle for 

 life under changing conditions, slight modilications of 

 instinct could hardly fail occasionally to be profitable 

 to individuals, I can see no overwhelming difficulty 

 on our theory. Even in the most marvellous instinct 

 known— that of the cells of the hive-bee — we have 

 seen how a simple instinctive action may lead to 

 results which fill the mind with astonishment. More- 

 over, it seems to me that the vei-y general fact of the 

 gradation of complexity of instincts within the limits 

 of the same group of animals, and likewise the fact 

 of two allied species, placed in two distant parts of 

 the world, and surrounded by wholly different con- 

 ditions of life, still having very much in common in 

 their instincts, supports our theory of descent, for 

 they are explained by it ; whereas if we look at each 

 instinct as specially endowed, we can only say that it 

 is so. The imperfections and mistakes of instinct, on 

 our theory, cease to be surprising ; indeed, it would 

 be wonderful that far more numerous and flagrant 

 cases could not be detected, if it were not that a 

 species, which has failed to become modified and so 

 far perfected in its instincts that it could continue 

 struggling with the co-inhabitants of the same region 

 would simply add one more to the myriads which 

 have become extinct. It may not be logical, but to 

 my imagination it is far more satisfactory to look at 

 the young cuckoo ejecting its foster-brothers, ants 

 making slaves, the larva of the ichneumida; feeding 

 within the live bodies of their prey, cats playing with 

 mice, otters and cormorants with living fish, not as 

 instincts specially given by the Creator, but as very 

 small parts of one general law leading to the ad- 

 vancement of all organic bodies — Multiply, vary ; let 

 the strongest live and the weakest die." 



The Stoat in Jersey.— Having just read in 

 Science-Gossip for July, 1883, that, " Some authors 

 seem to speak as though the stoat were never white 

 in England, but only farther north," I thought it 

 might interest some of your readers to know that 

 about seven or eight years ago my father shot one in 

 Jersey. It was seen running along a clay bank just 

 behind our house, and was shot from the staircase- 

 window ; the distance being so short the skin was 

 unfortunately much spoilt, and therefore was not 

 kept. The animal was perfectly white, with the 

 exception of a black tip to its tail. We sometimes get 

 strange visitants to the island, even a hoopoe having 

 been shot here about twenty-five years ago. — J. J. B. 



NOTES ON YEAST-FUNGI.* 



THE Saccharomycetes, or Yeast-Fungi, are uni- 

 cellular plants, which multiply themselves by 

 budding, and reproduce themselves by endogenous 

 spores. They live singly or united in bud-colonies, 

 chiefly in saccharine solutions, where they excite 

 alcoholic fermentation. 



In most of the Saccharomycetes the cells are round, 

 oval, or elliptic ; seldom are they elongated into 

 cylindrical tubes, which are divided by transverse 

 partitions, and may be regarded as the first indication 

 of the formation of hyphse, i.e. of a mycelium. For 

 the purpose of multiplication the cell forms an out- 

 growth, which is filled with a portion of the contents 

 of the mother-cell, gradually assumes the form and 

 size of the latter, and separates itself from it by a 

 wall. Both cells can in like manner produce fresh 

 daughter-cells, which often remain for a considerable 

 time united with one another, and on separation 

 continue to grow independently. 



The formation of spores succeeds most easily on a 

 moist solid substratum. Typically the whole cell 

 contents divide themselves into 2-4 roundish portions, 

 or contract into a single spherical body. The portions 

 of the contents surround themselves each with a 

 membrane, and so produce the spores, which can 

 bud like the vegetative cells. 



To the Yeast-Fungi (in the narrower sense) belongs 

 the capacity of decomposing the sugar of a fluid into 

 alcohol and carbonic acid, i.e. of exciting alcoholic 

 fermentation. 



The carbonic acid comes off in rapid streams of 

 bubbles, while the alcohol, as well as certain 

 subordinate constituents of sugar, remains behind. 



The fermentation proceeds most energetically with 

 restricted access of air ; but, if the air is excluded for 

 a long time, the yeast -cells perish. 



bACCHAROMYCETES. 



The same is true of the Saccharomycetes, especially 

 in a botanical aspect, as of the Schizomycetes. Just 

 as in the latter case, so also in this, is it necessary to 

 impose a limit upon the accepted species, and only 

 those founded by trustworthy investigators can be 

 considered. Of course there remain even then many 

 doubtful points ; for the majority of the now accepted 

 species of Saccharomycetes maybe only various forms 

 of one and the same species, which have become 

 differentiated by changed conditions of growth. 



XVI. Saccharomyces, Meyen. Unicellular fungi, 

 with vegetative increase by budding, and rejjroduc- 

 tion by spores, which, for the most part, arise by 

 subdivision of the contents of the mother-cell. 



* QTranslated from Dr. Winter's edition of the " Kryptoga- 

 men- Flora," with additions.] 



