444 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Most of the following experiments were made upon Stentor coeruleus. 

 This object has special advantages for the particular end in view. The 

 animal was found to have a high degree of sensitiveness to its environ- 

 ment. Its responses differed in kind, and especially in degree, with 

 variations in the reagents applied. Both the raising of cultures and the 

 experiments themselves showed that Stentor differs from some other 

 Protozoa in this respect. This fact permitted a much greater variation 

 of the experimental factors than a more uniform responsiveness would 

 have done. The qualities above described apply in its cell-division and 

 are probably due to the close relation between that process and metabol- 

 ism. The other interesting reactions of the animal were observed only 

 incidentally. 



II. General Methods and Technique. 



The methods and technique for experimentation upon Protozoa require 

 much consideration on account of the variety of conditions involved. 

 Usually each case requires special treatment, but in the following experi- 

 ments certain aspects of the subject were of such constant occurrence 

 that they may be dealt with once for all. Only the essential points 

 will be mentioned. 



Since these studies are chiefly concerned with metabolic problems, it 

 was necessary to maintain the animals experimented upon under condi- 

 tions as nearly normal as possible. Hence the first requirement was 

 some mechanical device for retaining Stentors in a given medium and 

 also for transferring them to it. For the former purpose the hanging- 

 drop method was used at first. Siuce many animals were required, a large 

 number of drops was necessary. Upon one side of a thoroughly cleaned 

 plate of thin glass (the thin glass used for photographic negatives an- 

 swers the purpose well) were placed numerous drops, each containing 

 from five to eight Stentors. With a quick motion this plate was inverted 

 over a shallow cylindrical glass vessel, half filled with water, the edge of 

 the vessel having been previously smeared with vaseline. The whole was 

 then placed under a dissecting microscope, a rough map of the field with 

 its contained drops was made, and the number of Stentors in each drop 

 written upon the map. When, after experimentation, the next count 

 was made, the record was continued upon the same map. With a little 

 practice it became easy to regulate approximately by the size of the 

 pipette used the number of Stentors put into a drop. This method was 

 practicable and expeditious for handling large numbers of individuals 

 and afforded excellent opportunity for any desired examination with ob- 



