32 AMEBOID MOVEMENT 



(eight or less) of long and very slender tapering pseudopods are 

 formed which usually persist for a long time (Figure 7, a, b}. 

 These pseudopods are frequently quite straight and regularly 

 disposed around the central mass of protoplasm (Penard, '02, 

 pp. 87, 89). In no case are any endoplasmic granules found in 

 these slender pseudopods; they consist entirely of hyaloplasm. 

 In retracting these pseudopods a curious phenomenon is sometimes 

 observed; the pseudopod is rolled up into several (as many as 

 six) turns of an almost perfect helical spiral of a diameter six 

 to eight times that of the pseudopod. But as the process of with- 

 drawal proceeds, the spiral becomes irregular, but parts of some 

 of the turns persist in the last vestiges preceding complete with- 

 drawal (Figure 7, b}. These spirals are also observed in other 

 species besides radiosa (see p. 128 seq.) 



Another species of ameba in which a trophic as well as a rayed 

 stage is found, is the recently described species bigemma. In this 

 species the rayed stage is only of occasional occurrence (Figure 

 8, ft). The larger the ameba is, the rarer is the rayed stage as- 

 sumed. On very rare occasions one finds a rayed stage in which 

 the pseudopods are long, straight, slender and tapering, and more 

 or less regularly disposed around the central mass of proto- 

 plasm. The trophic stage (Figure 8, a) is much the more com- 

 mon. In this condition pseudopods are formed in large number. 

 They are small, conical or linear, and blunt, and they do not de- 

 termine the direction of locomotion, as they do in proteus, dubia, 

 or laureata. These pseudopods are often composed only of 

 hyaloplasm, though frequently the basal parts of them consist of 

 endoplasm. When these amebas become suspended in the water, 

 they frequently assume a shape that approaches the rayed con- 

 dition ; six or more long conical pseudopods are run out from the 

 central mass of protoplasm, but the pseudopods are not straight 

 in this case, but irregularly curved and capable of being waved 

 about to a slight extent. The ameba readily passes from this 

 stage to the trophic. 



The species Amoeba bilzi (Figure 9) has come under my ob- 

 servation on several occasions, and its pseudopodial characters 

 are of considerable interest in this connection. In its usual form 

 this ameba has the general appearance of a sphaeronucleosiis. 



