559 
Ward. — Symbiosis. 
I think this line of inquiry may lead to results in the 
present connexion, as it is obvious that the products of 
fermentation of an organism A must be favourable, or without 
effect, or deleterious to the action of another, Z?, in its immediate 
neighbourhood. Moreover, it is shown that a product which 
is, per se, devoid of either favourable or deleterious action, 
may acquire the power of exerting one or the other if the 
concentration increases. 
Katz regards the action of sugars as not a purely chemical 
one, but as a physiological stimulus ; and without pretending 
to understand the distinction in detail, we may admit the 
importance of the experimental facts, and not only seek for, 
but also hope for, more light. 
Here, then, is a brief sketch of some of the salient features 
of symbiosis, and of some of the physiological factors con- 
cerned in the processes ; and though it is far from exhaustive, 
it may serve our purpose to-day of starting a discussion, and 
of showing some lines along which further investigation is 
desirable. 
Bibliography. 
1 . Frank : Ueber die biologischen Verhaltnisse des Thallus einiger Krusten- 
flecbten : Cohn’s Beitr. II, 1876. 
De Bary : Die Erscheinung der Symbiose : Strasburg, 1879. 
2 . Schwendener : Unters. iiber den Flechtenthallus, 1868, Naegeli’s Beitr. zur 
wiss. Bot., and Die Algentypen der Flechtengonidien : Basel, 1869. 
3. Bornet : Recherches sur les gonidies des lichens : Ann. des Sc. Nat., 1873. 
Famintzin and Baranetzky : Beitr. zur Kenntniss des selbstandigen Lebens 
der Flechtengonidien : Pringsh. Jahrb., Bd. vii. 
4 . Reinke : Sitzungsber. d. Kgl. Ges. d. Wiss.: Gottingen, 1871, Dec. 2; and 
Morph. Abhandlungen : Leipzig, 1873, p. 92. 
Janczewski : Bot. Zeit., 1872, No. 5. 
Leitgeb : Unters. iiber die Lebermoose : Jena, 1874, p. 23. 
Strasburger: Ueber Azolla : Jena, 1873. 
5 . Marshall Ward : Symbiosis and Symbiotic Fermentations : Trans. Institute 
of Brewing, January, 1892, No. 3, vol. v, p. 59. 
Kerner : Natural History of Plants (Engl. Ed.), vol. i, pp. 254 and 255, 
vol. ii, pp. 159 and 233. 
6. Vuillemin : Antibiose et Symbiose : Association Franfaise pour l’Avancement 
des Sciences. Paris, 1889. 
