PROTOZOAN FAUNA OF HAY INFUSIONS 25 
sufficiently comprehensive to rule out as far as possible individual 
variations and give final results of some general applicability; 
for, as Dujardin quaintly expressed his own experience with 
infusions :7 
Rien de plus simple que de préparer des infusions et d’y voir se pro- 
duire les Infusoires; mais rien de plus difficile que d’obtenir des résultats 
semblables de deux infusions préparées en apparence dans les mémes 
conditions: c’est qu’en effet les circonstances ne peuvent jamais étre 
exactement semblables. En supposant que la dose des ingrédients et 
la qualité de ces ingrédients soient les mémes, la température, l’état 
hygrométrique et l’état électrique, ainsi que l’éclairage, et l’agitation ou 
le renouvellement de lair, n’auront pas pu étre les mémes ou varier de 
la méme maniére dans les deux cas. Or, toutes les causes exercent sur 
le développement des Infusoires une influence qui, pour n’étre pas scien- 
tifiquement déterminée, n’en est pas moins bien réelle et souvent bien 
considérable. 
A. EXPERIMENTS 
Twenty-six infusions were made up with nearly pure timothy 
hay and laboratory tap water. In every case 20 grams of hay and 
5 liters of water were put into a glass battery jar with a capacity 
of about 53 liters. Each was loosely covered with a plate of 
glass to prevent undue evaporation and the entrance of dust. 
The jars were situated in a small room with windows on three sides 
so that all the infusions received practically the same illumina- 
tion. The temperature was recorded with a maximum and mini- 
mum thermometer. With this as the general plan, three methods 
of procedure were followed, giving three types of infusions desig- 
nated respectively, A, B and C. 
A Infusions. In this series the hay was boiled for five minutes 
in approximately 250 cc. of water and then sufficient tap water 
was added to make 5 liters. This infusion was then ‘seeded’ 
with 5 ce. of material from laboratory infusions and aquaria rich 
in animal and plant life. The ‘seed’ used in this series and in 
the following B series was thoroughly mixed in a flask before being 
added, so that each was seeded as nearly the same as possible. 
B Infusions. These were made up exactly the same as the A 
series, except that the hay was removed from the infusion by 
“Loc. cit., pp. 170-171. 
