270
Forms of Babesia Gibsoni (Patton) in the Dog
in a healthy animal is brought about by blood
inoculation. The latter can readily be explained
by the fact that the inoculum, in addition to
carrying the gametocytes, also carries the parasite
in a stage of fission, and this latter alone, in due
course, is able to produce a fresh infection (like
malaria and some other species of arthropod-borne
protozoan parasites). It should, however, be
emphasized that this point can only be clarified by
actual study of the stages of this parasite in the
body of the invertebrate host.
SUPPLEMENTARY NOTE ON THE SYSTEM-
ATIC POSITION OF THE PARASITE
By H. N. RAY, M.Sc., Ph.D. (Lond.)
SINCE Starcovici [1893] created the genus
Babesia, its precise systematic position and its
relationship with certain allied genera have been
subjected to a critical examination by several
workers in this field. Thus Franca [1917, 1918]—
as quoted by Wenyon [1926]—in classifying the
piroplasmata recognized several genera while Du
Toit [1918] accepted only six genera under the
family Babesiidae Poche, 1913, viz.
1. Babesia Starcovici, 1893
2. Nuttallia Franca, 1910
3. Nicollia Nuttall, 1908
4. Smithia Franca, 1910
5. Rosiella Nuttall, 1912
6. Gonderia Du Toit, 1918
On the other hand, Wenyon [1926] in critically
reviewing the whole position recognised only one
genus, Babesia, to include all the organisms des-
cribed under different generic titles in the family
Babesiidae, and, in his opinion, small variations
in size, shape and division into two or four daught-
er individuals should not be considered as suffi-
cient grounds for the retention of these generic
names. But this remark made by Wenyon is not
tenable, since more recent observations have
shown that the inclusion of Babesia mutans of
cattle and Babesia sergenti of ovines by Wenyon
under the genus Babesia is no longer justifiable,
as these organisms are referable to the family
Theileriidae Du Toit, 1918. Again the inclusion
of Nuttallia equi under the genus Babesia will per-
haps not be a correct step, because, both morpholo-
gically and pathologically, these two parasites are
quite different from each other. Donatien and
Lestoquard [1930] entirely disagree with Wenyon
and adopt the family name Piroplasmiidae to
include these organisms. Under this family they
recognise two genera, viz. Piroplasma and Nutta-
llia. The genus Piroplasma is further divided
into two sub-genera, namely (1) Piroplasma and
(2)Babesiella. In their scheme of classification,
hey have, in addition to considering the morpholo-
tcal char acters, paid equal attention to the biologi-
cal features and pathogenicity of these various
organisms and also to the action of certain drugs
upon them. In commenting upon this scheme.
Thomson and Hall [1933] observe that, if such
characteristics as reaction to drugs, etc. were
'adopted generally for the classification of genera,
it would obviously become necessary to reconsider
the subdivisions of the genus Trypanosoma and
other protozoa'. Sergent, Donatien and Lestoquard
[1935], however, in their classification of cattle
Piroplasma have pointed out that the generic name
Babesia, being preoccupied by a genus of bacteria
proposed by Trevisan in 1889, can no longer be
used for another protista and that the generic
name Piroplasma Patton 1895 should be adopted
instead. They, too, have considered the action
of certain drugs on these parasites and their lack
of immunological identity as important factors
in classifying the cattle Piroplasmata. This result-
ed in the recognition of two sub-genera, viz. (1)
Piroplasma, in the strict sense and (2) Babesiella.
According to their observations, the organisms,
such as B. canis. B. caballi, should be known as
Piroplasma canis and P. caballi.
The question whether the action of certain drugs
on the parasite should be considered as a factor
strong enough for their generic or specific dif-
ferentiation amongst themselves is still unsettled,
and it is difficult to resist the force of the above-
mentioned argument put forward by Thomson and
Hall [1933] with regard to the classification of
trypanosomes. From the literature extant on the
subject it is clearly seen that there exists a good
deal of confusion with regard to the nomenclature
of generic or subgeneric titles of various parasites
which according to Wenyon should all be accom-
modated under the genus Babesia.
Clarifications
of all the existing confusions is indeed a tremendous
task, but it is not the object of the present note.
The parasite under discussion belongs to the
suborder Piroplasmidea, because it inhabits red
blood-corpuscles and does not form the pigment
characteristic of some of the members of the
suborder Haemosporidiidea. In
the existing
scheme of classification, Piroplasmidea is divided
into two families, viz. Babesiidae and Theileriidae.
These two families, according to Wenyon, are de-
fined as follows :
'Family : Babesiidae—Parasites which multiply
in the red blood corpuscles by division into two or
four*. They are of varying size and shape and
have a tendency to arrangement in couples of pear-
shaped individuals*. The forms in the corpuscles
are asexually reproducing individuals and possibly
gametocytes.
Genus: Babesia Starcovici, 1893.'
*Italics are mine.