578 Buller.—Contributions to our Knowledge of the 
employed, much briefer swarm-periods would certainly result 
than would be the case if the spermatozoa were liberated 
in hanging drops of tap-water. With similar conditions it 
seems not improbable that there would be no great difference 
in the length of the swarm-periods of Gymnogramme Lau - 
cheana and G. Martensii. 
Weak solutions of alcohol 1 made with tap-water were found 
to be less deleterious than the distilled water. Thus in 
i*5 gm per cent, the spermatozoa move as long as in tap- 
water. In two experiments the times of longest movement 
were determined to be two hours fifty-eight minutes and three 
hours twenty-five minutes respectively. In each case the 
majority of spermatozoa moved well for about 100 minutes. 
With increasing concentration, however, the injurious effect of 
the alcohol becomes obvious. Thus in 6 -9 gm per cent., 
although the spermatozoa move rapidly at first they come to 
rest in fifteen minutes. The fact, however, that the movements 
last so long in such concentrated solutions of alcohol proves 
that this substance is not so toxic as is often supposed. 
In glycerine I have been unable to detect any toxic action. 
When spermatozoa are liberated in a hanging drop of 13-8 
gm per cent, (the solution being made with tap-water) they 
are at first motionless, but after a few minutes begin to move 
slowly, gradually obtaining a maximum speed. It is pro¬ 
bable that during this process the glycerine penetrates into 
the protoplasm. Some spermatozoa, however, do not recover 
and never move in these strong solutions. Although the 
motion is not so lively the swarm-period is quite as long in 
13*8 or 6-9 gm per cent. 2 glycerine as in tap-water. 
Acids are very toxic. Malic and tartaric acids are about 
equal in their effects. Thus at o-oi gm per cent, the sper- 
1 In these experiments, as in all those made with the glass rings, the chamber 
was about half filled with the solution of which the hanging drop was made. 
2 In some experiments with this concentration movement still took place more 
than four hours after removal of the prothallia from the drops. Since some of 
the spermatozoa may have begun to move after lying some time motionless in the 
glycerine it cannot be assumed without further experiment that they swarm longer 
in a solution of glycerine than in tap-water. 
