112 
CritJudia” cleti 
extremity (Fig. 2). The latter form closely resembles “ Herpetomonas ” 
in the position of its nuclei and the absence of an undulating mem- 
bi'ane. 
A typical parasite, however, is that represented in Fig. 1. In this 
large flagellate form the flattened leaf-like shape of the body is 
extremely well shown towards the posterior extremity, which displays 
a slight spiral twist. The cytoplasm is quite free from any of the 
granules so commonly found in related species. The tropho-nucleus 
is situated slightly towards the posterior end. Occasionally it presents 
the appearance of a densely staining central karyosome surrounded by 
a layer of more diffusely staining chromatin (Fig. 5). More often, 
however, it seems to consist of numerous chromatic granules arranged 
either irregularly (Fig. 1) or in a linear series (Fig. 4). The 
kineto-nucleus is usually situated immediately in front of the tropho- 
nucleus and slightly to one side of the middle line. In close relation 
to it a small but distinct end-bead may usually be seen, situated 
at the apex of a small vacuole which lies immediately in front 
of the kineto-nucleus (Figs. 5-7). From the end-bead arises the 
flagellum running forward along the surface of the body, where it forms 
a distinct undulating membrane, until it becomes free at the anterior 
extremity. The dimensions of a typical flagellete form are as follows: 
total length from the posterior extremity to the tip of the flagellum, 
25/r; breadth, 2/r ; total length of flagellum, 16 p,; length of free part 
of flagellum, 4 p. 
Various stages in the division of the flagellate forms are represented 
in Figs. 6-11. The first sign of the process may usually be seen in the 
kineto-nucleus or its associated end-bead (Figs. 6-8). All the details of 
this division cannot be followed in the preparations before us but the 
kineto-nucleus seems to elongate and then constricts into two daughter 
nuclei (Figs. 6-8). The end-bead divides independently of the kineto- 
nucleus (Fig. 8) and from the new end-bead another flagellum arises 
(Figs. 9, 10). The new flagellum thus arises independently and is not 
formed by the splitting of the original one. By the time that these 
divisions are complete the tropho-nucleus usually shows signs of dividing, 
often evidenced by the arrangement of the intra-nuclear granules in two 
longitudinal rows one at each side of the nucleus (Fig. 9). The tropho- 
nucleus then divides into two equal daughter nuclei (Fig. 10) and by 
the time this division is complete the new flagellum is usually well 
developed. When the latter reaches the anterior end, the body of the 
parasite begins to split into two daughter parasites, this splitting always 
