General Survey 



15 



as well as in earlier years. It is admitted that some of these 

 lower creatures appear to be extraordinarily simple as 

 compared with trees, birds and men: such are evidently the 

 bacteria among plants; such are amoeba and its relatives 

 among animals (see Figure 1). But in some of the Proto- 



Figure 1. Simpler forms of Protista, a to g, Diverse kinds of bac- 

 teria, after Zopf, Engelmann and Fischer, h, Amoeba radiosa, after 

 Leidy. 



zoa we find an astonishing complexity of structure (Figure 2, 

 Figure 3) and of function, so that some of the students of 

 the group, like Dobell (1911), maintain that there is no 

 ground for calling these organisms "simple" or "lower" or 

 even "unicellular": that they are merely small organisms, 

 diverse in their plan of structure from the larger animals 

 and plants. But it appears evident that amoeba? and bac- 

 teria are structurally simpler than vertebrates, in that they 

 consists of fewer kinds of differentiated parts; and this 

 seems to me true even for the more complex Protozoa, when 

 compared with the Metazoa. They may therefore be 

 properly called simpler or lower organisms, meaning thereby 

 that they have fewer differentiated parts than the higher 



