452 
H. M. WOODCOCK AND O. LAPAGE. 
We have considered it useful to discuss the possible 
relationship of Sole nomas tix to the flagellates, because not 
only does our parasite differ in many respects from any 
bacterial protist of which we have knowledge, but it also 
appears to incline more to the Protozoa in one or two 
important features. In the first place, the host of ordinary 
bacteria may be at once dismissed fi-om consideration. Dr. 
Ledingham has kindly looked at the parasites and entirely 
agrees with us in this opinion ; moreover, as above mentioned, 
cultures made on various media were quite unsuccessful. The 
most striking feature of Selenomastix, from a bacterial 
point of view, namely, the presence of a large flagellum, 
easily visible in life and by ordinary staining methods, is 
only met with, so far as we are aware, in the case of one 
or two very large spirillai* forms and among certain Sulphur- 
Bacteria^^ (Ehabdomonas, Ophidomonas), of which a 
good account has been given by Biitschli (‘Arch. Protistenk.,^ 
vol. i, 1902, p. 41). The spirillar forms and Ophidomonas 
have a flagellum at each end, Rhabdomonas a single, 
terminal one. In these forms, too, the flagellum shows a 
tendency to split up, in a somewhat similar manner, into 
fibrils of varying thickness. These forms have also a well- 
marked envelope (periplast), which stand off well from the 
body in many cases; that of Rhabdomonas is spirally 
striated, a point Avhich we have never seen in Seleno- 
mastix. 
It is possible that the origin of Selenomastix is to be 
sought amongst this type of organism ; we have had it tested 
for the presence of sulphur, howevei*, with entirely negative 
results. Moreover, Selenomastix certainly appears very 
far removed from the spirillar type as generally recognised. 
Taking first the points of agreement, there is, of course, the 
transverse division and the absence of a definite, constituted 
nucleus. Another feature which is somewhat against the 
Protozoan character of our parasite is the peculiar homo- 
geneous appearance of the protoplasm ; the ordinary true 
flagellates, for instance, which occur in the rumen, look very 
