136 E. A. MENCHIN AND II. M. WOODCOCK. 



active, did we notice auythiiig comparable to the rounded-off 

 phases described by Miss Robertson (17). It is probable that 

 the percentage of individuals which undergo this alteration 

 on the slide is very small compared with the number that do 

 so when the parasites pass into the leech. 



The trypanosomes in our permanent preparations show 

 considerable differences in size. On Giemsa-stained smears 

 the largest individual observed has a total length of 72 fx and 

 a breadth of 5"6 n, including the membrane. The correspond- 

 ing diuiensions of the smallest form seen are only 55 fi by 4 fx 

 (fig. 83). These two extremes are connected by intermediate 

 forms of varying size (cf. figs. 34, 35). The average size 

 works out at about 67 ^ by 5*2 ^. The free flagellum varies 

 from about 10 fx to 15 fi, with an average length of 13 //. The 

 length of the fiagellum does not seem to stand in any very 

 close relation to the size of the parasite, and now and again 

 IS shorter in a large individual than in one of intermediate 

 size. The largest trypanosome noticed on "wet'' films 

 stained with iron-hoematoxylin is drawn in fig. 53; it is a com- 

 paratively wide, plump individual, which would probably 

 have seemed even wider on a Giemsa-stained smear. It 

 measures 65 fx by <o-Q fx. It is probably somewhat longer in 

 reality, for the free flagellum, which is unusually short in the 

 drawing, comes into contact, at the point where it apparently 

 ends, with a corpuscle Avhich is stained deep black ; although 

 it probably runs across this for some distance, its course 

 cannot be followed. Other parasites on iron-ha^matoxylin- 

 stained films are seen in figs. 52-56. They are mostly a little 

 shorter than the parasites on " dry " films ; this difference is 

 most noticeable in comparing the body-protoplasm, for the free 

 flagellum itself is in most cases actually longer and averages 

 14-8 ^ against 13 jx on the dry smears. "We are inclined to 

 think this is due to the contraction of the general cytoplasm 

 to a greater extent than the entire flagellum (i. e. the flagellar 

 border + free flagellum) in iron-ha?matoxyliu films. 



There is another rather interesting point brought out by a 

 comparison of the trypanosomes fixed and stained bv the 



