﻿Trypanosoma found in Pontobdella. 



93 



apart, and show each a connection to the kinetonuclei, not 

 1 only by means of the modified cross-bar, but, in addition, 

 each by a fine red line to the distal portions of the kineto- 

 I nuclei. These last-mentioned lines appear to me to corre- 

 ; spond to the outer pair of the four lines described above as 

 joining the cross-bar in the earlier stage (Fig. 31) to the 

 I kinetonucleus. 



In a later stage the kinetonuclei have moved apart and 

 the flagella are already projecting from the spindle-shaped 

 J preflagellar bodies (Fig. 33). They grow out as fairly thick 

 prolongations, and are in the living state at first very stiff 

 and non-motile ; they do not invariably keep time, one 

 flagellum sometimes being considerably in advance of the 

 other. If the relative positions of the kinetonuclei and the 

 ■ I flagellar spindles is observed in Figs. 35 and 31, it will be 

 ; ! seen that the separation of the former, as shown in Fig. 35, 

 i ' has brought about a rotation in the position of the spindles, 

 I so that now their distal ends point towards each other. 

 < The spindles, it is now seen, are still bound to the kineto- 

 i j nucleus by two slender threads (Fig. 36, etc.). (These 

 i j threads do not show, as a matter of fact, in Fig. 35, but are of 

 j quite definite and constant structure, though very delicate.) 

 ; ' Fig. 47 illustrates this point more clearly. It is about this 

 j i stage, ix,, when the preflagellar bodies are removed from 

 each other, that the red cross-bar is no longer to be 

 'i distinguished. 



Division of the trophonucleus and protoplasm now take 

 place. The preflagellar bodies still persist, and it is at this 

 stage, in very delicately stained individuals, that a certain 

 ' amount of detail may be seen in these structures. Figs. 38 

 and 39 illustrate this period in the development, a review 

 of the proximal part of the flagellum in these individuals 

 suggesting that the flagellum has grown out from the central 

 part of the preflagellar spindles. It is impossible, however, 

 to be sure of a point of this kind where the detail is so 

 \\ extraordinarily minute. 



The body of the animal now begins to lengthen out, and 

 I the kinetonucleus gradually moves back behind the tropho- 

 nucleus, drawing the flagellum with it. The preflagellar 



|i 



i < 



