C. Dobell and M. W. Jepps 
345 
(Johannsen) such as have been demonstrated to exist in almost all 
species of organisms which have hitherto been studied systematically^. 
We have obtained no evidence that races of E. histolytica producing 
cysts of any particular size are characteristic of infections acquired in 
any particular locality. We have found cysts of the commonest size 
(ll/x-14p,) in carriers who contracted dysentery in all parts of the world 
from which we have examined cases (Europe, Asia, Africa, and America). 
The strains producing small cysts have been detected similarly in cases 
from many parts of the world (France, Egypt, Glallipoli, Salonica, 
Mesopotamia, India). Cysts of the larger diameters have been found in 
the stools of dysentery patients from Egypt, Clallipoli, Salonica, China, 
Thibet, Malay States, and S. Africa. It is not of course possible to say 
that the infection was acquired in every case when and where the attack 
of dysentery occurred, though this appears probable in many cases. 
We have pointed out elsewhere (1917) that the name “E. minuta” is 
improperly applied to those races of E. histolytica which produce cysts 
of small size. We think it necessary to emphasize this once more, since 
the contrary has again been asserted by Woodcock (1917). He says “the 
name ‘minuta’ should be reserved for the distinctly small type or 
variety, the cysts of which are only about 8 microns in diameter.” There 
can be no question however that the 2 iame Entamoeba minuta was given 
by Elmassian (1909) to the common race of E. histolytica producing cysts 
of large size (about 12p. in diameter). It follows, therefore, that minuta 
is a synonym without validity for histolytica-, and if the name '''minuta” 
is retained for any stage in the development of this parasite, then it must 
be applied only to the small precystic amoebae, characteristic of sub¬ 
acute infections, which were described and figured by Elmassian and to 
which he gave the name. 
^ Comparable instances in the Protozoa are to be seen in the two species Paramecium 
caudatum and P. aurelia. It has been sho'wn by Jennings (1908) that within each of these 
species there are numerous strains whicli differ from one another only in the average size 
of their constituent individuals. It is true that in this case the characters distinguishing 
the pure lines from one another are those of the organisms themselves—not of their cysts. 
In the case of E. histolytica we are still uncertain whether the full-grown amoebae belonging 
to strains producing cysts of different size arc themselves likewise distinguishable in the 
same respect. (The precystic '^minuta" forms of the different strains undoubtedly corre¬ 
spond in size to the sizes of cysts which they produce. Cp. Plate VI. Figs. E. h. (2) and 
E. h. (3), and see also our earlier paper, 1917.) Nevertheless, whether this be the case or 
not appears to us immaterial, since the size of the individual or the size of the cyst might 
be used with equal propriety to discriminate races from one another. A summary of the 
literature bearing upon pure lines in the ciliate Protozoa has been published elsewhere by 
one of us (C. D. 1914). 
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