2 E. J. LUND 



INTRODUCTION 



While studying the phenomena of regeneration and structural 

 regulation in Bursaria, it became desirable to know something 

 of the relations of this organism to its food and of the processes 

 which the solid food material undergoes in its passage into and 

 through the cell and in the elimination of residues. This paper 

 aims to present the first part of these observations and to make 

 a general survej^ of the relations of this organism to food, leading 

 up to a more detailed study of these and certain other problems 

 of the cell as found in this unicellular animal. 



Bursaria was found to be much more favorable for the investi- 

 gation of these phenomena than the smaller infusoria such as 

 Paramecium. No study has heretofore been made of the rela- 

 tions of Bursaria to food, so that the facts herein presented are 

 new. The present investigation attempts not onl}^ to determine 

 quahtatively whether the relations to food are similar to those 

 more or less known for Paramecium, Stentor, Vorticella and 

 other infusoria, but more particularly to work out and express 

 these relations in a more quantitative wa}^ than has been done 

 heretofore. It was found that certain kinds of experimental tests 

 such as those on the rate of digestion, could be made upon this 

 form, which it would have been difficult or impossible to carry 

 out on smaller unicellular organisms. Its \'ery large size offers 

 a singular opportunity for easy manipulation in many kinds of 

 work. When in a clear medium it is readily \'isible to the naked 

 eye at a distance of six or eight feet and individuals may be 

 transferred singly with a pipette without the aid of any magni- 

 fying instruments. 



Bursaria occurs not infrequently in cultures brought from 

 ponds in the vicinity of Baltimore, though it is less common 

 than many other Protozoa. It can readily be cultivated in large 

 culture dishes in the laboratory. In this way I have had abun- 

 dant material at my disposal for many months. The method 

 of cultivation has been simply the inoculation of an infusion of 

 timothy hay in tap water from the wild culture; by several in- 

 oculations at different times one usually succeeds in obtaining 

 large numbers. Since the food of this organism is not bacteria, 



