N. H. SWELLENGREBEL 
123 
This last stage resembles the degenerating preflagellate form repre¬ 
sented in Diagram VII (Fig. 5). 
It may be noted that Prowazek does not mention the preflagellate 
stages in his construction of the life-cycle of Herpetoinonas muscae- 
domesticae and so a confusion with these stages was quite possible. 
During the “ pai’thenogenesis ” the nucleus is divided into two large 
and two small nuclei, just as in Diagram XII, Fig. 3. The result of 
this development is the formation of small non-flagellate cells each 
containing a nucleus and a blepharoplast. According to Patton’.s 
nomenclature we should call these stages simply post-flagellate forms. 
It seems probable that Prowazek in his “ parthenogenetic ” and 
“ etheogenetic ” cycle has put together forms which have no close 
relation to each other. Until further confirmation is forthcoming these 
cycles should be regarded with some suspicion. 
IV. General Remarks. 
1. Similarity in structure of some Bacteria and 
degenerating Flagellates. 
Stages of degeneration such as are figured in Diagram XI 
(Figs. 1, 2, 4), where the nucleus becomes diffuse (often forming a 
chromatic band wound in a more or less distinct zig-zag line) and 
a general lack of differentiation of the internal cellular structure may 
be noted (Fig. 1), seem to be frequent among trypanosome-like 
flagellates. Similar changes were noted in Trypanosoma leiuisi in the 
blood of the rat (Swellengrebel, 1910), and in the gut of different 
invertebrate hosts (Swellengrebel and Strickland, 1910). 
Robertson (1906) has noted a zig-zag line of chromatoid substance 
(volutin) passing through the body of Trypanosoma hriicei, but here the 
nucleus remains unaltered and only volutin-granules are expelled from 
it. Robertson has already drawn attention to the analogy of these 
zig-zag structures of Trypanosoma and similar chromatoid filaments in 
Spirochaetae (Perrin, 1906 ; Swellengrebel, 1907 ; Fantham, 1908) and 
bacteria (Swellengrebel, 1906-1909; Dobell, 1908-1909; Guilliermond 
1909; Mend, 1911, etc.). The diffuse nuclei of T. leiuisi and Herpeto- 
monas calliphorae bear a remarkable resemblance to the chromatin- 
spirals of many bacteria (e.g. Bacillus flexilis ; B. hinida of Dobell; 
Sphaerotilus natans of S^'eUengrebel) much more than the above 
mentioned chromatoid filaments of T. brucei. The value of this analogy 
