Inter-Relationships of Protista and Primitive Fungi. 97 
constitute the Protista par excellence in the sense that they include 
forms combining the characters usually regarded as distinctive of 
plants and of animals, one might feel tempted to suggest their 
removal from the Protozoa but for the fact that they are separable 
from the Sarcodina by nothing more than the presence of a flagellum 
in the adult phase. For instance, Mastigamceba combines the 
characters of the Flagellata and of the Amceba-\ike Sarcodina in 
having an amoeboid body which bears a flagellum, and it is placed in 
the Flagellata merely because the flagellum is retained throughout 
life instead of being present only in the young states as is the case in 
many of the Sarcodina. Biitschli regarded the Pantostomatineae 
(the group including Mastigamceba and its allies) as representing 
the common ancestral type of the Protozoa, the flagellate young 
stages of many of the Sarcodina being considered as recapitulative 
larval stages. On this view the flagellum is regarded as a primitive 
organ, but a general objection similar to that raised in the case of 
the chromatophore arises here—it seems natural to suppose that 
flagellate organisms must have been preceded in evolution by others 
not possessing so definite an organ as the flagellum. However, this 
objection is to some extent weakened by the occurrence among 
various groups of what may fairly be regarded as transitional organs 
between flagella and pseudopodia, as well as between flagella and 
cilia. As pointed out by Minchin, more knowledge with regard to 
the nature and formation of the flagellum is needed in order to 
decide this point, and—since flagella are borne by many Bacteria 
which are on general grounds considered to be primitive organ¬ 
isms—particularly with regard to the question whether the flagella 
of Bacteria are of the same nature as those of Protozoa. 
The Sarcodina, in the wide sense, are usually divided by 
zoological writers into six groups. The Mycetozoa (Myxomycetes) 
are distinguished by their tendency to the aggregation or fusion of 
the cells into more or less complex resting-groups or fructifications, 
and by their reproduction by flagellate or amoeboid zoospores. 
The remaining groups, in which there is no such aggregation into 
plasmodia or fructifications, are separated chiefly by the characters 
of the pseudopodia. In Rhizopoda these are simple or if branched 
not coalescent, and are either blunt or if fine at the ends are 
dilated at the base. In Foraminifera they branch freely and 
coalesce to form networks. In the three other groups they are 
fine to the very base, are radially arranged, but rarely coalesce : 
in Heliozoa they have a central filament, in Radiolaria (body 
divided into a central and a peripheral part by a structure termed 
the central capsule) and in Proteomyxa (no central capsule) there 
- is no central filament. No sharp lines can be drawn between these 
six groups ; there are many genera which are by some systematists 
placed, for instance, in the division Filosa of the Rhizopoda, from 
their slender pseudopodia, and by others in the Foraminifera ; while 
the division Proteomyxa is frankly admitted to be simply “a sort 
of lumber-room for forms which it is hard to place under Rhizopoda 
or Flagellata, and which produce simple cysts for reproduction, not 
fructifications like the Mycetozoa” (Hartog, 1909). 
The Sporozoa, which are parasitic in higher animals, are usually 
intracellular for part at any rate of their life cycle, rarely possess 
pseudopodia or (except in the male gametes) flagella, and reproduce 
