666 Blackman .— The Primitive Algae 
We see from this section that though Chlamydomonas is 
the most primitive of Algae, yet it has an elaborate organiza¬ 
tion which should be accounted for by its descent; so in the 
next section we shall seek for light upon the evolutionary 
origin of this foundation-stone of the vegetable kingdom. 
Section III. Flagellata. 
Until recent times investigators of the lower organisms 
strove to find a dividing line between those that ought to be 
classed as plants and those that must be regarded as animals. 
Attempts to base such a distinction on any single test- 
character resulted in groupings that were most obviously 
unnatural. The last and best of these characters in which 
hope was put, was the distinction between the methods of 
nutrition in the two kingdoms, but this also fails as a clue to 
a natural separation 1 . 
The only scientific method of procedure is now recognized 
to be the inductive one. By this the organisms, such as they 
may be found to be, are grouped together by a consensus 
of their characteristics in small natural groups, and these 
again into larger aggregates. This, of course, in itself is by 
no means an easy matter, and until it had been approximately 
accomplished it could not be determined how far a line could 
be drawn between the two kingdoms without doing violence 
to these induced natural groupings. 
Knowledge, however, gradually comes to hand, and it is 
certain that by no set characteristics can the distinction between 
plant and animal be pushed right down as a fundamental 
cleavage-line without separating otherwise closely allied 
genera and doing similar violence to natural groupings. 
In the sea, of low forms of life (Protista) that intervene 
between the contrasted and undisputed plant and animal 
kingdoms, certain groups have been found by inductive 
investigations to stand out well characterized. The most 
striking of these, to the botanist at least, is that of the 
1 A few forms with well-developed chromoplasts, as Chromulina, ingest solid 
food. 
