﻿92 



Proceedhigs of the Royal Physical Society. 



connection with some such form as Herpetomoiw.s mitscoe 

 domesticce, where the flagellum persists as a double structure, 

 i.e., is composed of two flagella joined by a narrow membrane.^ 

 In the form at present being considered, it operates simply 

 as a precocious division. Stage 3 has been described first, 

 as it is a very definite condition and explains the earlier 

 development. Stages 1 and 2 of the development of the 

 preflagellar bodies appear to be represented by Figs. 28 

 and 29.2 Fig. 28 (stage 1) shows a loDgitudinal division 

 having taken place in the kinetonucleus ; this, it will be 

 seen, has occurred in the opposite direction from the 

 ordinary division of this body, which is transverse. One 

 is, however, prepared for this by the appearance of what I 

 have called the cross-bar. 



In stage 2 (Fig. 29) the segment of the kinetonucleus 

 farther away from the trophonucleus has taken the form of 

 an oblong body composed of two thick little vertical bodies. 

 These are joined by two horizontal cross-bars. I consider 

 this structure to be the early stage of the preflagellar body, 

 and interpret it as presenting a so far incomplete transverse 

 division, the method in some points closely resembling the 

 normal division of the kinetonucleus to be described later. 



I am not clear as to when exactly the anterior of the 

 horizontal cross-bars shown in Fig. 29 disappears. The two 

 vertical bodies (arising from the distal segment of the 

 original kinetonucleus) each grow out into a little rod or 

 spindle-shaped bundle of fibres (Figs. 30, 31), which may 

 perhaps be interpreted morphologically as mitotic figures. 

 The fibrillar character of the finally developed flagellum 

 may sometimes be most strikingly demonstrated in crushed 

 or slightly macerated specimens. 



The next stage is represented in Fig. 32, and shows the 

 kinetonucleus just divided. The red cross-bar has altered in 

 appearance, and now presents two little thickenings at its 

 central part. The preflagellar bodies are beginning to move 



^ See Prowazek, "Die Entwicklung von Herpetomonas," Arb. a. d. 

 kaiserlichen Gesundheitsamte, Bd. xv. Heft. 3, 1904. 



- Stages 1 and 2 are very difficult to find ; they are probably passed 

 through more rapidly than the later stages. 



