ON PBLOMYXA VIRIDIS. 367 



resemble those figured for P. palustris. "When one of these 

 large pseudopodia is about to be extruded the movements 

 aflfect very deep-lying portions of the protoplasm ; a wave-like 

 bulging occurs, which gradually pushes out in a radial direc- 

 tion ; an active current passes outward along its centre ; all 

 the protoplasmic contents in the neighbourhood are carried 

 outwards and, having arrived at the extremity, pass back again 

 in the peripheral portions of the pseudopodium, which thus 

 narrows while it is elongating. The whole process gives one 

 strongly the impression that the impulse for the extrusion is 

 central and deep-lying in its origin. It is not that a small 

 pseudopodium is gradually increased in size, but the mass of 

 protoplasm extruded is actually greatest at first and then 

 gradually diminishes. Even when fully extruded the back- 

 ward peripheral currents still continue, especially in the 

 proximal portion of the pseudopodium, which thus becomes 

 flask-shaped, joined to the main portion of the organism by a 

 narrow neck. 



All this time no peripherally placed colourless layer ap- 

 pears, the vesicles and other protoplasmic contents being 

 pushed on up to the surface ; but when this pseudopodium 

 commences to retreat the contents pass backward faster than 

 the protoplasm itself, and a colourless superficial layer is left. 

 Fig. 3 represents the distal extremity of a pseudopodium 

 which has just commenced to retreat. If this withdrawal is 

 rapidly continued some of the colourless protoplasm will be 

 left sticking to the glass. 



Besides these large pseudopodia, small ones are often found 

 which seem to take their origin in the superficial layer. In 

 these latter the hyaline protoplasm is first protruded, and into 

 this a number of the bacteria appear to burst out, followed 

 almost at once by some of the vesicles, which often sepa- 

 rate a good deal from one another and appear as so many 

 isolated spherical green droplets ; these are sometimes fol- 

 lowed by the other protoplasmic contents (fig. 5). These 

 pseudopodia are never prolonged to any extent. 



The rate at which the large pseudopodia are protruded is 



