of Edinburgh y Session 1883-84. 
275 
observed that there remains not one morphological type merely, to 
be discriminated as Protozoa, but three — the ciliated, amoeboid, and 
plasmodial, — all, indeed, physiologically analogous in exhibiting 
movements (a phenomenon of which pure morphology takes abso- 
lutely no cognizance), but as distinct in form from each other as from 
the encysted form. The utter confusion which has too long main- 
tained as to the distinction of plant and animal life is thus seen to 
be due to the want of that discrimination of morphological from 
physiological considerations, which is now happily nearly complete 
in the study of higher organisms. In short, though the encysted 
and usually non-motile cells or cell-aggregates may be conveniently 
termed plants by the physiologist, and though usually non-encysted 
and motile cells or cell- aggregates may similarly be grouped as 
animals, — yet the morphologist, distinguishing form-history from 
life-history, must recognise among the Protista four main lines of 
differentiation, or four series, which may perhaps conveniently be 
termed Protojphijta, Rhizopoda, Ciliales, and Plasmodlales. (See 
Plate IV. figs. 1-13 in first series.) 
5. Phytogeny of Protista, — On this view also there is no necessity 
for the assumption lately coming into view of the origin of the 
Protista from several distinct stocks, or for accepting, with Bergh,* 
so specialised a form as Peridinium as a type of the primeval 
Protozoon, for all are naturally derivable from a simple Myxomycete 
or Protomyxoid ancestor. Of course, this view by no means excludes 
the possibility of the remoter and simpler Protamoeboid progenitor 
assumed by Haeckel. 
6. Relation of the Protoghytes to the Higher Plants, — Transverse 
division may of course occur in the encysted, amoeboid, or ciliated 
stage of the life-cycle of a cell. When this takes place chiefly in 
the encysted state the tough and coherent wall holds the resultant 
cell-aggregate together ; this cell-aggregate soon becomes moulded by 
the force of the environment into some definite form ; and what we 
term a vegetable organism (a Metaphyte corresponding to a Meta- 
zoon) is the result. 
But the cells of our multicellular plant do not lose their tendency 
to cycle. Alike in linear, superficial, or solid aggregates, the cycle is 
* Bergh, ‘‘D. Org. d. Cilio-flagellata,” Morph. Jahrh.. vii. 2; Abstract 
by T. J. Parker, N, Z. Jour, of Sci., October 1882. 
