THE EFFECT OF EXCRETION PRODUCTS OF INFUSO- 

 RIA ON THE SAME AND ON DIFFERENT SPECIES, 

 WITH SPECIAL REFERENCE TO THE PROTOZOAN 

 SEQUENCE IN INFUSIONS 



LORANDE LOSS WOODRUFF 

 Sheffield Biological Laboratory, Yale University 



It is well known that a hay infusion presents a kaleidoscopic 

 series of phenomena from its inception until it finally reaches a 

 stage of sterility, or, in the presence of sunlight, of practically 

 stable equilibrium in which animals and green plants become so 

 adjusted that a veritable microcosm exists. In an attempt to 

 elucidate some of the complex factors involved in the faunal and 

 floral changes of typical infusions a series of observations of a 

 considerable number of infusions was made,i and the following 

 conclusions, among others, were reached : 



1. In hay infusions, seeded with representative forms of the chief 

 groups of Protozoa, there is a definite sequence of appearance of the 

 dominant types at the surface of the infusion, that is. Monad, Colpoda, 

 Hypotrichida, Paramaecium, Vorticella and Amoeba. 



2. The sequence of maximum numbers and of disappearance is identi- 

 cal with that of appearance, except that apparently the position of 

 Amoeba advances successively from the last (sixth) place to the fifth 

 place and then to the fourth place. 



.3. Emphasis is put upon the strictly biological interrelations (for exam- 

 ple, those involving food and specific excretion products) of the various 

 forms as the most important determining factors in the observed 

 sequence. 



The interdependence of the organisms of a hay infusion is so 

 complex that, taken as a whole, it is quite beyond the possibility 

 of analysis, and accordingly the logical method of approach to 

 the subject was to study the effects of isolated organisms on them- 

 selves and on each other. The first essay in this direction con- 



1 L. L. Woodruff, Observations on the origin and sequence of the protozoan 

 fauna of hay infusions. Jour. Exp. Zool., vol. 12, no. 2. 



575 



