SS4 The Unity of the Organism 



in the background of consciousness as though he had before 

 him for comparison a cat and a hen, for instance. Do the 

 figures give the impression that one presents a very simple 

 animal wliile the other represents a very complex one? 

 Which, may well be asked, is the very simple one? Does 

 one give the impression that it represents an organless ani- 

 mal, while the other represents an animal with organs? 

 Does one seem organized while the other is unorganized? 

 Does one look like a true animal while the other is an un- 

 true or pseudo-animal? Yet there is now unanimity among 

 zoologists that the creature represented by figure 1 is a 

 protozoan, while that represented by figure 2 is a metazoan. 

 The protozoan sliown is a species of Ciliate which inhabits 

 the stomach of the ox. Its techincal name is Diplodinium 

 ecaudatum. The figure is from R. G. Sharp. Figure 2 

 is of the common fresh water hydra. 



Or compare in detail a Stylonychia, a protozoan, with a 

 Stenostoma, a worm. For the former, the description and 

 figure of Stylonychia mytilus, figure 3, given by Hartog in 

 the Cambridge Natural History will serve our purpose well. 

 A good description of a Stenostoma, figure 4, is furnished 

 by Ott. A rough and ready way of estimating the degree 

 of complexity of the two animals is to notice the number of 

 named parts or organs in the two descriptions, presumably 

 intended to be about equally thorough. 



The activities of these two species have also been well 

 studied, so they can be compared from this as well as from 

 the anatomical standpoint. To any one who has watched 

 both creatures somewhat attentively in their normal lives, 

 the great animation and diversity of movement of the pro- 

 tozoan as contrasted with that of the metazoan are striking 

 enough. Concerning the general character of the movements 

 of Stylonychia, Hartog writes, "It moves through the water 

 either by continuous swimming or by jerks, and can either 

 crawl steadily over the surface of a solid or an air surface 



