214 
Macrostoma mesnili N. Sp. 
to the encysted forms of Trichomonas described by Ucke, Bohne and 
Prowazek and in greater detail by Bensen. In the present instance 
a most careful search failed to reveal any Trichomonas. However 
intermediate forms such as are shown in Plate XVI, Fig. 9 were 
frequently encountered so that it appears most probable that these 
peculiar bodies are derived from the flagellates. They occur in an 
almost endless variety, only a few of which are shown in Plate XA r I, 
Figs. 9—13. Many of them are undoubtedly degenerate forms and all 
stages up to complete disintegration were met with. It seems most 
probable that these bodies are products of an abnormal development 
ultimately terminating in death. During this abnormal development 
vacuolations, changes in shape, segmentations of the body and various 
nuclear divisions of a peculiar type take place. Bodies with many 
nuclei may be formed but these all have the appearance of being 
abnormal. In the light of the fact that undoubted cysts (Plate XVI, 
Figs. 7 and 8) occur it seems impossible to arrive at any other 
conclusion. 
The supposed Cysts of Trichomonas. 
Bodies similar to these are constantly to be met with in human 
faeces. They may occur together with Trichomonas, and it is this 
association which has led Bohne and Prowazek and more recently 
Bensen to describe them as developmental cysts of these flagellates. 
Within these cysts a most complicated nuclear reduction and autogamy 
ai’e described by these observers. These bodies may occur in association 
with Trichomonas but sometimes they are present in enormous numbers 
when no Trichomonas can be found, while at other times they bear no 
proportion to the number of Trichomonas present. If faeces containing 
these so-called cysts be kept either at laboratory temperature or at that 
of the body complete degeneration takes place within a few days. It 
has never been found possible to produce any development of these 
cysts outside the body on the warm stage as can be done with the cysts 
of Entamoeba coli. Further the origin of such a cyst from a living 
Trichomonas has never been followed though many attempts have been 
made to do so. It seems impossible to associate these structures with 
the flagellates unless as abnormal and degenerate forms. It is possible 
that such bodies can arise in another manner. Dobell has suggested 
that similar bodies, described by Prowazek as flagellate cysts from the 
intestine of lizards, are merely yeast cells and he has also thrown some 
