Physiology of the Spermatozoa of Ferns. 573 
still for a while in a fairly straight line. After a few minutes 
the spermatozoon moves once more at the normal rate and 
in the normal manner. The latter may be roughly described 
as a revolution in more or less complete circles about an 
ever-changing centre. I have noticed the above facts a con¬ 
siderable number of times in experiments with concentrated 
solutions. Recovery has taken place after a spermatozoon 
has been motionless for five minutes. Cessation of move¬ 
ment and death are therefore by no means necessarily simul¬ 
taneous, as has been previously assumed 1 . 
In order to determine the manner in which movement is 
affected by concentration the following method was used. 
Glass rings (10 mm high x 20 mm broad) were fastened upon 
microscope slides by means of a mixture of wax and fat, 
and fitted with cover-glasses. A little of the solution to be 
tested was poured into the chamber, and a hanging drop 
made. To the latter a single prothallium, after being well 
washed in part of the same solution, was added. The cover- 
glass was sealed with vaseline. By this method the sperma¬ 
tozoa were directly liberated into the solution to be tested. 
The solution could not alter appreciably in concentration, and 
oxygen had free access to it. 
The solutions were made isotonic with 1, y 1 ^, Fr an ^ 
mol potassium nitrate. The solvent was tap-water. 
In Table V, F indicates that the spermatozoa moved forward, 
C „ „ only the cilia moved, 
O „ „ there was no movement at all. 
At the two highest concentrations of the salts and sugar 
spermatozoa were only rarely set free. The experiments 
were carried out with the spermatozoa of Gymnogramme 
Mar tens ii. In the case of alcohol, potassium nitrate and 
cane-sugar similar results were obtained on repetition with 
the spermatozoa of Pteris serratula. 
1 Pfeffer, loc. cit., Bd. i, p. 385. 
