654 
epicyte is thinnest in the median line and very thick on each side of the 
median line, i. e., at the base of the papilla. This variation in the 
thickness of the epicyte produces the appearance in optical section of a 
small canal opening to the outside. This structure has been recognized 
by several observers in other species of Stenophora. Lieidy* in his 
description of Gregarina larvata = Stenophora larvata, calls attention 
to this apparent canal as follows: “Superior cell placed in a depression 
of the inferior, surmounted by a slight papilla in which may be detected 
two lines apparently the outlines of an oral canal to the interior of the 
cell which is filled with granular matter’. This he shows in his fig. 17. 
Schneider figures the same type of a structure for Stenocephalus juli 
= Stenophora juli. The explanation for this apparent canal in the pre- 
sent species and perhaps for the other species of Stenophora, is found 
in the expansion of the papilla, the thickened portion of the epicyte 
serving to form the base of the papilla and to concentrate the strain of 
the sarcocyte against the thin median portion which becomes inflated, 
as it were, by the sarcocyte. 
By a comparison of figs. 2 and 3 it may be seen that there are five 
steps in the expansion of this papilla. 1) A thickening of the collar 
region around the septum which renders the protomerite more globose. 
2) An increase in the distance between the endocyte of the protomerite 
and that of the deutomerite. 3) A change in the shape of the anterior 
margin of the endocyte of the protomerite from concave to convex 
toward the papilla. 4) A reduction of the space occupied by the sarco- 
cyte in the anterior portion of the protomerite. 5) The enlargement of 
the papilla. 
From this sequence of changes it was concluded that the contrac- 
tion of the gregarine in the region of the septum, perhaps throughout 
the whole of the protomerite, forced the sarcocyte into the extreme end 
of the protomerite and inflated the thin median portion of the epicyte 
forming the projecting globose papilla. This view is further substan- 
tiated by the shape of the expanded papilla. The globose end of the 
papilla with the narrow neck joining it to the anterior end of the proto- 
merite is precisely of the shape assumed by an elastic membrane held 
across a slightly projecting tube and inflated from the inside. 
Unfortunately material was not at hand to investigate the function 
of this expansible papilla. Should it be shown that it were a prehensile 
structure by means of which the gregarine could anchor itself, it might 
contribute to the understanding of the elaborate type of epimerite as is 
4 Proc. Acad. Nat. Sci. Philad., Vol. IV, p. 231, 1848—49. 
5 Arch. Zool. exper., 4, PI. XX, figs. 29, 30, 32, 33, 1876. 
