450 
H. M. WOODCOCK AND G. LAFAGE. 
region, when preseiit, as representing chromatin or some 
allied substance diffused in an extremely fine condition 
throughout a relatively large area of the protoplasm ? 
Secondly, as regards the first type of ovals and the 
crescents, there are several reasons for concluding that these 
are only distinct phases of one parasite. There is the fact 
that, on all occasions save one, we have found the two forms 
associated, and possibly in the case of the third goat ovals 
may have been present, but were so scarce in comparison with 
the enormous number of crescents that we did not notice 
them. Important points of agreement between the two 
types as regards appearance, one mann'er of movement, 
structure, the occurrence of crescents 'without a flagellum, 
and so on, have been already dealt with. Lastly, in the case 
of some individuals, it is purely a matter of choice whether 
to regard them as bean-like crescents, or as'bean-like ovals; 
thus the form drawn in fig. 38 is readily derivable, one may 
reasonably suppose, from an aflagellate crescent such as that 
of hg. 36, while on the other hand, between the parasite of 
fig. 46 and the oval of fig. 45 there is equally little difference. 
Concluding, then, that the above-described different forms 
all belong to one parasite, it still remains a matter of uncer- 
tainty what is the order of transition between them, respec- 
tively, and how the different phases should be combined 
into one life-cycle ; it appears very probable that the 
crescents can give rise to ovals ; but we have no indications 
as to whether the ovals become crescents. Further, we are 
inclined to the view that the second type of ovals pass into 
the first type, rather than vice versa. 
The Nature and Affinities of Selenomastix rumin- 
autium. — It will be apparent from the foregoing account 
that this new parasite does not fall readily into any of the 
known groups of organisms included under the designation 
Protista; in many respects it is an altogether new type of 
organism. On first seeing the living, active crescents, with 
their conspicuous, long flagellum, we naturally thought we 
had to deal with a new member of the flagellates, as, indeed. 
