STUDIES ON PARASITIC PROTOZOA. 
301 
The Pellicula. 
One of the most characteristic features of Polymastix is 
the thickened periplast or pellicula, which gives the body a 
certain rigidity and' stiffness, and prevents any metabolic 
altering of shape. Sometimes the empty periplast is found 
persisting after the disappearance of its softer contents. 
A distinct gap in its continuity may be observed at the 
extreme anterior end ; this gap marks the position of the 
cytostome. The surface of the periplast is raised up into a 
number of thickened ribs or ridges cotes of French 
authors), which stain deeply with iron-haematoxylin. These 
are not continuous from end to end of the body, but, while 
approximately parallel to the long axis, they fall into little 
groups of two or three, often inclined at considerable angles. 
Grassi suggested that these structures, which appear as dark 
striations in stained preparations, might be trichocysts ; 
Kunstler held them for adherent bacteria. Sometimes the 
periplast may be seen fraying off, so that the ribs^’ project 
from the surface, when they look very like adherent bacilli 
(PI. 18, figs. 12 and 14). 
Hamburger compares these striations with thickenings in 
the periplast of Euglena. 
Now, it is of interest to find that such pellicular thickenings 
are eminently characteristic of the Trichonymphid. ^^Fiir 
die meisten Gattungen ist das Auftreten von Stabchenfor- 
migen Bildiingen in der Pellicula charakteristisch^’ (Dofiein, 
1911). Lophomonas striata, Biitschli, in particular, is 
provided with a thick, striated periplast, and Janicki’s 
excellent account and figures (1910) leave no doubt that 
this structure presents the same general characters as in 
Polymastix 
^ Alexeieff shares my opinion as to the affinities between Poly- 
mastix and the Lophomonadidse — “ Le genre Polymastix pouiTa 
etre place dans la famille des Lophomonadidse, on tout an moins con- 
sidere comme une forme de transition entre les Polymastigines et les 
Lophomonadidse (Trichonymphines) (1912).” 
