TRANSACTIONS OF SECTION B. 70t 
agent which determines their association. And hitherto apparently no case has 
been met with in which a substance has been observed to give way to a pair of 
organisms, neither of which can attack it singly. 
19. The assimilation of nitrogen by plants, which is believed to take place in the 
symbiotic growths found on the roots of the Leguminose, is a phenomenon of which 
at present no explanation can be given, as this element cannot enter into combina- 
tion with either hydrogen or oxygen unassisted ; its absorption must take place in 
a circuit in which changes occur from which the necessary energy may be derived. 
As hydrogen is liberated in many fermentations, it appears not improbable that 
nitrogen may be brought into circuit by acting as a hydrogen depolariser ; one 
function of the nodule may be to supply carbohydrate, which is fermented by the 
bacteroid in circuit with the nitrogen. 
20. Symbiosis, as distinguished from parasitism, involves the conception not 
only of the concurrent existence of organisms, but of their useful concurrency ; 
indeed, any other form of symbiosis is difficult to imagine, and antzbiosts is a con~ 
tradiction in terms. It is desirable that we should remain satisfied with the term 
until our knowledge of the actual character of the changes involved in ordinary 
as well as in symbiotic fermentations is far greater than is now the case: at 
present it is impossible to draw valid distinctions. 
Note.—The explanation of fermentation adopted in this note is given in my 
address to the Chemical Society in 1895.!_ Green, in his recent: work on Enzymes, 
speaks of Baeyer having put forward, in 1870, the hypothesis that fermentation 
is due to electric hydrolysis. This is incorrect. Baeyer’s paper is entitled ‘ Ueber 
die Wasserentziehung und ihre Bedeutung fiir das Pflanzenleben,’ &c. He makes: 
no reference whatever to the manner in which water might be withdrawn, but 
merely shows that the withdrawal of water and the subsequent addition of its: 
elements in a different order would produce effects such as are observed in 
fermentations. 
Discussion. 
Dr. H. Van Laer (Brussels).—Revient sur les communications faites par M. le 
professeur Marshall Ward et le Dr. Armstrong. Il fait remarquer que l’exemple 
de vie en commun d’une moisissure et d’une levure, telle qu'on la retrouve dans. 
Vintéressant procédé de fermentation de M. Calmette, ne rentre nullement dans les 
cas de symbiose, métabiose ou antibiose signalés par M. Marshall Ward. 
Il est incontestable que dans cette association de moisissure et de Ievure. 
celle-ci y trouve tout avantage, puisqu’elle se borne a utiliser le sucre produit par 
les diastases de la mucédinée. Mais cette derniére ne trouve guére d’avantages. 
dans cette société. Il y a plutét ici un cas de parasitisme analogue a celui qui se 
présente lorsque le Mycoderma cerevisie se trouve en méme temps qu'une levure 
dans un milieu nutritif contenant un sucre (la saccharose ou la maltose, par 
exemple) que le mycoderme ne peut utiliser. 
Il a remarqué que lorsque cet organisme vit en concurrence avec la levure il 
sempare d'une portion des monosaccharides qui se forment par l’action des 
diastases levuriennes sur la maltose ou la saccharose. 
Professor R. Warington.—AlN joint life is based on division of labour. The 
bricklayer cannot do his work unless the brickmaker supplies bricks, and the brick- 
maker will cease to work if his bricks are not consumed. We must not argue that 
there is no combined work because all the agents do not simultaneously attack the 
same material. There is an evident need, however, of defining the sense in which 
the term Symbiosis is used: at present it is applied to a number of distinct 
cases. It will be well to follow Professor Marshall Ward’s proposal, and to limit. 
the use of the term to those cases in which each living organism is essentially 
benefited by the work of its companion, so that joint life is needed for the welfare 
of both. Cases in which B prepares material for A, but derives no essential benefit. 
from A, should be termed, as Professor Ward suggests, not Symbiosis, but. 
Metabiosis. 
1 Trans. p. 11236. 
