PROTOZOAN FAUNA OF HAY INFUSIONS papal | 
able to a wider consideration of many transient species which 
appear apparently at random, for, if it is possible to reach any 
conclusions of value from the study of these few dominant forms, 
it may open the way for an explanation of the seemingly fortuitous 
distribution of the remaining species. 
A tabulation of the fauna of the infusions showed that the first 
analysis of the results should consider the following groups and 
genera of Protozoa: Monads, Colpoda, Oxytricha and various 
closely related hypotrichous forms, Paramaecium, Vorticella, and 
Amoeba, because all these organisms were present in practically 
every infusion. The term ‘monads’ is used in a broad sense to 
include several different genera and a multitude of species of 
small flagellate Protozoa usually classified under the generic names 
Oikomonas, Monas, Bodo, ete. Colpoda cucullus is the most 
common member of the genus Colpoda which has appeared in the 
infusions. Occasionally the form of the organism has not agreed 
exactly with the specific description usually given, and it may well 
be that some of these organisms properly rank as other species of 
the genus, but as this could be determined only by following out 
the life history of the animals, it was necessary to assign the forms 
merely to the genus. In a number of cases species of Colpidium 
was found intermixed with the Colpoda. Colpoda and Colpidium 
are apparently adapted to practically identical conditions of the 
infusions and consequently it matters little which form is chosen 
for study. Since Colpoda has usually appeared in greater abun- 
dance than Colpidium, it has been selected, as the representative 
of this type of ciliate, for detailed study in this work. Among 
the hypotrichous ciliates which appeared, Oxytricha was prob- 
ably the most common, but closely associated with this genus 
was Stylonychia, Urostyla, Gastrostyla, ete., and therefore the 
various species of these genera were considered as a unit and are 
designated in this work as ‘Hypotrichida.’ Also several members 
of the Vorticellidae appeared, nearly all of the genus Vorticella. 
The term ‘ Vorticella’ accordingly is used to include all true mem- 
bers of this genus regardless of species. The same is true of the 
term ‘Amoeba’ as here employed, this name being used to include 
such forms as Amoeba guttula, radiosa, etc., as well as typical 
Amoeba proteus. ‘Paramaecium’ is applied to two species, 
