Physiology of the Spermatozoa of Ferris. 553 
results. The explanation of the terms employed is as 
follows :— 
A —marked attraction. R=repulsion, 
a = weak attraction. o = indifferent. 
rA = repulsion at first, afterwards strong attraction. 
N= spermatozoa did not collect in the tubes. 
- =no experiment made owing to low solubility or 
acidity of substance. 
The third column contains the molecular weights of the 
salts employed. 
When a tube is filled with a solution of a neutral salt 
which gives a marked attraction (A), the concentration 
being mol, a few minutes after the beginning of the 
experiment the spermatozoa are seen collecting at the mouth 
of the tube and also just inside in considerable numbers. 
In this diffusion-zone the spermatozoa move backward and 
forward for some seconds or minutes, being alternately 
attracted and repelled. It is only after repulsion from a 
certain diffusion-zone within the tube has taken place several 
times that the majority of spermatozoa finally enter deeply 
into the solution. Within one minute after penetrating down 
the tube they come to rest owing to the withdrawal of water 
from their protoplasm by the salt solution. Being heavier 
than the solution they quickly sink to the bottom of the tube, 
where they may be easily counted. The collections of sper¬ 
matozoa amount to 100-1000, according to the number 
liberated from the prothallia and the specific action of 
each salt. 
When a neutral salt which attracts is tested at a concen¬ 
tration isotonic with T mol potass, nitrate a weak attraction 
(a) usually takes place. The spermatozoa enter the tube 
without hesitation at the mouth, the repulsion described 
above not making itself evident. The attraction, however, 
only lasts a few minutes. The spermatozoa collect in smaller 
numbers. They continue their motion in the tube, and when 
are much more like those here employed than would have been the case if distilled 
water had been used. 
