562 B idler .—Contributions to our Knowledge of the 
proteids and sugar—on which the tube lives, are also em¬ 
ployed 1 in giving the chemotropic stimulus. On the other 
hand, the spermatozoa of the Ferns have stored within them 
sufficient energy to reach the oospheres without the help of 
any additional food-supply from without. It is therefore not 
essential that the substance (or substances) liberated from the 
archegonia should possess a high value as food. Malates 
might therefore be employed to attract the spermatozoa. 
The acid radicle of malic acid is present in a decoction 2 of 
prothallia, and is doubtless a normal product of the meta¬ 
bolism of the cells. This fact helps to explain why in all 
probability a malate is set free from the archegonia in order 
to attract the spermatozoa. 
The dissociation theory and chemotaxis. The theory of 
electrolytic dissociation of solutions has been successfully 
employed in estimating the toxic effect of various substances 
upon higher plants 3 , Bacteria 4 , and Fungi 5 . 
The first suggestion that chemotaxis may to a certain 
extent be elucidated by the dissociation theory is due to 
Ostwald 6 . This physical chemist explains the fact, discovered 
by Pfeffer, that the salts of malic acid attract the spermatozoa 
of Ferns with about equal strength, whereas the diethylester 
does not attract at all, on the supposition that in the salt 
solutions the negative radicle is free as an ion, and in this 
form attracts, while in the ester solution it is not free, this 
substance being undissociated. 
In a recent paper by Jennings 7 , entitled ‘The Laws of 
chemotaxis in Parameciuml an endeavour was made to 
1 Lidforss, loc. cit. 2 Pfeffer, Bd. i, p. 417. 
3 Kahlenberg and True, On the toxic action of dissolved salts and their electro¬ 
lytic dissociation. Bot. Gaz., Vol. XXII, 1896, p. 81. Heald, On the toxic effect 
of dilute solutions of acids and salts upon plants. Ibid., p. 125. 
4 Kronig u. Paul, Die chemischen Grundlagen der Lehre von der Giftwirkung 
u. Desinfektion. Zeit. f. Hygiene u. Infect., Bd. xxv, 1897, p. 1. 
s Clark, Electrolytic dissociation and toxic effect. Jour, of Phys. Chern., 
Vol. Ill, 1899, p. 263. 
6 Ostwald, Referat, Zur Pharmakologie des Quecksilbers, E. Dreser, Zeit. f. 
phys. Chem., Bd. xiii, 1894, p. 378. 
? Jennings, Study IV. loc. cit.. May, 1899. 
