INTRODUCTION 



nucleus does not alter its position, though constant move- 

 ment is observed among the constituents of the granular 

 part. Connecting the nucleus with the base of the 

 flagellum is a bell-shaped tract free from granules, 

 which takes when stained a rather darker colour than 

 the surrounding cytoplasm.* The whole swarm-cell is 

 enclosed by a layer of hyaloplasm of extreme tenuity over 

 most of the surface, but thicker at the posterior end, where it 

 often extends in a brush of two to eight more or less slender 

 pseudopodia. In addition to the dancing motion, which is 

 maintained as long as they are free in the water, the swarm- 

 cells when they come to rest exhibit movements of an amoe- 

 boid character, and spread with an irregular outline ; or they 

 assume a linear form and 

 creep over a level surface 

 with a snail-like motion, 

 the flagellum being ex- 

 tended in advance. In 

 this position the move- 

 ment of the interior sub- 

 stance is seen to advantage, 

 In the large swarm-cells of 

 Amaurochaete fuliginosa it 

 may almost be described 

 as streaming, the granules 

 passing from one end to 

 the other in constant flow. 

 Thehyaloplasmic extension 

 at the posterior end con- 

 tinually changes its form Flg 

 and it is here that refuse 



■mn+tp.ri<5rli«pViflr0-prl Aftpr nucleus by karyokinesis. Magnified 1200 times. 

 mallei IS CUSCnargea. Alter Drawn f rom stained preparations in Canada 



a time the creeping move- balsam. 

 ment is again exchanged for 



the dancing. In all cultivations of germinating spores, a 

 number of the swarm-cells, after a short period of activity, 

 withdraw the flagellum and become encysted in a globular 

 form (the microcysts of Cienkowski). After being dried and 

 re-wetted, the contents burst the membranous cyst-wall, which 

 remains as an empty hyaline sac, and emerge to resume their 

 activity. If bacteria are introduced into a cultivation of 

 swarm-cells on the stage of the microscope, they are seen 

 to be laid hold of by the pseudopodia and drawn into the 

 interior of the swarm-cells, where they are enclosed in a 

 digestive vacuole. Several bacteria are brought in turn to 

 the same chamber, or fresh captures are conveyed into one 

 or more additional vacuoles. The protrusion of pseudopodia 



Plenge, " Geisselglocke " Jahn in Ber. Deutech. Bot. Gesell., 



2 — Amaurochaete fuliginosa Macbr. 



a to /. Successive stages in bipartition of 

 swarm-cell, accompanied by the division of the 



* " Verbindungssttick 

 xxii. 86. 



a! 



;* 



