94 AMEBOID MOVEMENT 



great power of contractility and the speed with which contraction 

 may occur in Biomyxa, a fresh water foraminifer, have already 

 been mentioned (Figure 12, p. 47). Similar observations have 

 been recorded by other observers, recently by Schultz ('15), who 

 compares the contractility of foraminiferan pseudopods to that 

 of rubber bands. In fact as one watches the movements of a 

 Biomyxa, for example, under moderately high magnification, one 

 gains the impression that there seems to be no restriction im- 

 posed upon the extent of contractility in the pseudopods. They 

 seem to possess perfect elasticity. As to the transformation of 

 endoplasm into ectoplasm, little can be said, owing to the trans- 

 parency of the protoplasm. But the whole of the pseudopod, 

 when forming, seems to stream forward. As in Difflugia, the 

 interior streams flow at about the same rate as the pseudopod as 

 a whole advances. The highly developed power of contractility 

 however demands rapid changes in phase of the colloidal system, 

 and also a thick consistency. The behavior of pieces of the 

 pseudopodial network, when cut from a Biomyxa, shows clearly 

 that the protoplasm is actually thick, as compared with that of an 

 Amoeba proteus. When a Biomyxa is contracted into a spherical 

 mass, the interior exhibits continual rapidly streaming movements. 

 Some of these are rotational but most of them are radial. All 

 of the streams frequently change their direction and extent. No 

 corresponding changes are visible in the outer peripheral layer. 

 Among plants, some of the algae possess ameboid protoplasts 

 at one stage or another of their life cycle, but the details of 

 streaming have not been made out. It has been reported however 

 that the zoospores of some parasitic fungi move to all appearances 

 exactly like small amebas. We likewise lack details of the stream- 

 ing of the myxomycete plasmodia. From a more or less cursory 

 examination of a small aquatic plasmodium of undetermined 

 species, it appeared that the formation of pseudopods and the 

 process of streaming were quite different from similar processes 

 in the foraminifera. The pseudopods do not act independently as 

 in foraminifera. At almost the same moment the protoplasm 

 begins to flow from the pseudopods in a large section of the 

 plasmodium and into another section; then soon thereafter the 

 protoplasm flows back again. This oscillatory streaming is con- 



