STRUCTTJKE AND DIVISION OF TRICHOMONAS 



123 



B. Size 



Wenyon ('07) called attention to the great variation in size 

 in the Trichomonas of mice giving the length as from 3 to 20 n. 

 Kofoid and Swezy ('15) emphasized a similar variation in size 

 for T. augusta. In both cases the authors raise the point that 

 differences in size alone do not furnish sufficient criteria for the 

 separation of species. I have found two species in mice which 

 do differ as to size, and it may be that the range of sizes observed 

 by Wenyon had a greater significance than he supposed. Care- 

 ful study and measurement of the flagellates found in mouse 

 no. 1, for example, revealed a larger species which I take to be 

 T. muris, ranging in length from 8 to 20/x, with an average of 



12.9m, and a smaller species ranging in length from 6 to 9iu, with 

 an average of 7.2ju. The smaller species may be T. parva 

 Alexeieff, and can be differentiated on morphological grounds 

 other than size, and shows only three chromosomes in division. 

 In other mice pure infections of each species "were found as well 

 as other mixed infections. 



Measurements have been made from several series of slides, 

 and the results indicate slight racial differences for the different 

 hosts as well as differences due to various methods of fixation. 

 Table 1 indicates some of these differences. 



The results for different fixatives is strikingly illustrated by 

 mouse no. 24, where the average length for animals fixed with 

 Allen's fluid (15.7m) is 22.6 per cent more than the average 

 length for those fixed in Schaudinn's fluid (12.8m). It is prob- 



