181 
clusions, and they recognised that they were dealing with a part only 
of the parasite’s life-history. It would seem also from Pérez’s re- 
searches, since he apparently had a considerable amount of material at 
his disposal, that any other stage must be rare. 
In the younger parts of the cyst, the cell outlines, it will be noticed 
(figs. 2 and 8) are less definite, so that the appearance of a plasmodium 
is suggested, whereas in those parts where cell inclusions have appeared, © 
the cell walls are quite distinct, as was noted by Pérez. Cases of nuclear 
division, however, are non-existent unless figs. 2 and 3 represent such, 
and the appearance of a centrodesmose in (fig. 2, a) is indistinct. Care- 
ful search was made in the surrounding tissues for loose spores descri- 
bed by Pérez as being found within phagocytes, but none were found, 
Fig. 4. 
Fig. 2. Fig. 3. } 
e le À > o 
iR fre 
i. @ N ae ©. È 
fo : “ x 
$ SS Fig. 5 
= e.. À ay 
a. FR Se 
le) en e 
Fig. 2. Portion of section showing wall on the right and nuclear division (?) at (a). 
x 2700. 
Fig. 3. Portion of section showing young cells often without definite cellwalls, and 
also older cells with definite cellwalls and inclusions. X 1300. 
Fig. 4. Late stage in nuclear division (?). Cystwall on right. X 2700. 
Fig. 5. Older cell with cell inclusion. X 2500. 
and this also tends to show that the cysts dealt with in this paper were 
less advanced in development than those seen by Pérez, in some of 
which the cyst wall had ruptured. It will be seen from figs, 1, 2 and 4 
that the cyst wall is thicker than figured by Pérez but that may be 
due to the difference in the host. In any case I agree with him that the 
wall bears the appearance of having been secreted by the parasite and 
not by the host, the outer border being more definite than the inner. 
To sum up, there are at present known two stages of Dermocysti- 
dium. The one, described in this paper, consists of a plasmodium or a 
mass of ill-defined cells within a cyst wall, while the next stage shows 
a collection of distinct cells, each with a peculiar cell inclusion, and it 
is at this stage that the individual cells or spores (?) are set free by 
rupture of the cyst membrane. The fact that at one stage of its hfe- 
