If all the known species of amebas in which the necessary characteristics have been recorded, were arranged similarly with respect to the firmness and the thickness of the ectoplasm, the general relations of the various kinds of pseudopods in the list would be approximately the same as in the list given above; but there would appear an exception here and there, indicating the operation of special factors. Such an exception, for example, is seen in _proteus_ in the list of species given, which because of the ridges that it forms (Figure 3) has a smaller number of pseudopods than would be the case if no ridges were formed[2]. It may be concluded, then, that the number and character of pseudopods depends in large part upon the ectoplasm-forming capacity of the ameba; and that this property is intimately associated with the degree of fluidity of the whole mass of protoplasm in the ameba. [Illustration: Figure 10. Graph representing the relation of firmness and thickness of the ectoplasm with the number and character of the pseudopods in different species of amebas. _a_, the average maximum number of pseudopods directing locomotion in the different species of amebas. _b_, the number of transitional pseudopods. _c_, the number of static pseudopods. _d_, the estimated degree of firmness and thickness of the ectoplasm of the various species of amebas, grading that of _limicola_ as 1 and that of _verrucosa_ as 6.] That the number and character of pseudopods formed depends _in large part_ upon the firmness and thickness of the ectoplasm was said advisedly. For observations indicate that there are other factors which influence the character of pseudopods besides those which also control the formation of ectoplasm. These other factors indicate their presence readily in the details of structure of the pseudopods. Thus the number of directive, transitional or static pseudopods may be the same in two particular species, yet in their intimate structure and appearance they are always found to differ. In _bigemma_, _bilzi_ and _radiosa_, for example, the number of static pseudopods when formed is about the same in the three species, but the similarity ends there. For these species differ in the frequency with which pseudopods are formed, in their persistence when once formed, in the ratio of length to average diameter, in the general shape, in the frequency with which straight pseudopods are formed, in the speed of their formation and withdrawal, in the manner of their withdrawal, in their disposition with respect to geometrical pattern, in the character of the bases of the pseudopods, in the form of the free ends, and so on. Many of these characteristics are still further analyzable into numerous other and more detailed characters. And what is true of the static pseudopods is likewise true of the transitional and the directive. Pseudopod formation is however only a small part of the activity of an ameba. The formation of uroidal