566 Buller.—Contributions to our Knowledge of the 
does not attract the spermatozoa. It is still less astonishing 
that asparagin, which may be written as an amide-derivative 1 
of malic acid, does not attract, for not only is this compound 
practically undissociated, but the group of atoms which 
forms the negative radicle of malic acid is no longer present. 
Five sulphates have been tested, namely, those of sodium, 
potassium, ammonium, magnesium and caesium. They all 
attract. From what has already been said about the ions 
Na + and NH* it follows that we must attribute the attraction 
of sulphates to the negative radicle. It seems, therefore, very 
probable that the ion SOr attracts. 
A similar argument may be applied to the phosphates and 
tartrates. Their attraction is probably due to the respective 
anions. 
With regard to the ions of other neutral salts, there is not 
sufficient evidence to draw any very definite conclusions. 
From the fact, however, that sodium formate, sodium sulphite 
and sodium thio-sulphate attract, it appears probable that the 
respective anions give a positive chemotactic stimulus. There 
is at present no evidence to indicate the action of the ions 
Br~, I”, GOT, C2H3O2 - and C 2 0 ±. 
The eight undissociated substances tested namely, cane 
sugar, grape-sugar, lactose, amylodextrin, alcohol, glycerine, 
asparagin and urea, agree in not attracting the spermatozoa. 
The indifference of the carbohydrates is remarkable, in view 
of the fact that the spermatozoa of the Mosses are attracted 
by cane-sugar. Undissociated substances may yet be dis¬ 
covered which attract the spermatozoa of Ferns. Such 
substances will probably not be found among sugar or 
alcohols, owing to the fact that cane-sugar, grape-sugar, 
lactose and amylodextrin on the one hand and ethyl-alcohol 
and glycerine on the other act indifferently. 
A comparison may now be made between salts and acids. 
In Table II it will be seen that sodium malate attracts at the 
concentrations isotonic with T V, xo~o> toVo? an d tttooit m °l 
1 Asparagin is, however, to be regarded as the monamide of amido-succinic acid. 
Hollemann, Lehrbuch d. organ. Chemie, 1899, p. 221. 
