﻿Trypanosome found in Pontobdella. 



89 



highly refractive, and takes the stain very deeply, so that it 

 is very difficult to get a clear view of its detailed structure. 

 In shape it is oblong, and very often presents the appearance 

 of a rod (Fig. 12) split along its longitudinal axis. It is not 

 a perfectly simple structure, but appears to be made up of 

 several chromatic elements. This body is, on the vs^hole, 

 pretty constant in its appearance, much more so than the 

 similar organ in Trypanoplasma horrelli as described by 

 Keysselitz,^ still even here variations occur. Sometimes 

 (Fig. 6 and Fig. 54) the kinetonucleus is circular and gives 

 indication of a structure not unlike that of the trophonucleus : 

 it has, however, been so far impossible to count the number of 

 chromatic thickenings, as the details are always very obscure 

 (Figs. 3-13, etc.). Occasionally there may be a certain 

 amount of a substance taking on a blue colour in the kineto- 

 nucleus. Sometimes, too, a little granule may be detected in 

 the centre of the kinetonucleus, as in Figs. 34, 35, but these 

 points are very inconstant and very difficult to make out : 

 they are most obvious when the kinetonucleus is about to 

 divide. Of course, in questions of such fine detail, adven- 

 titious appearances, due to difference in staining, are very apt 

 to cause confusion. 



Another modification occurs through the deeply staining 

 material of the kinetonucleus becoming concentrated into 

 two or more little aggregations ; these stain almost black, 

 while the remaining parts take on a homogeneous bright 

 red with the Eomanowsky stains (Fig. 7). This appearance 

 is not at all frequently met with, and has probably to do 

 with the physiological relation between the kinetonucleus 

 and the protoplasm. Keysselitz observed an exactly similar 

 phenomenon in the kinetonucleus of T. horrelli. 



There appear, however, to be very generally two sub- 

 stances present in the kinetonucleus, one of which stains 

 more deeply than the other. What I have described as the 

 split-rod appearance of the kinetonucleus is a very common 

 feature in the larger rounded off individuals and in the forms 

 immediately derived from them. It is curiously suggestive 

 of a double or composite structure, but I am at a loss for an 



^ Arch. f. Protistenkunde, Bd. vii., 1906. 



