4; INTRODUCTION. 



be distinguished from the rest of the hyaline element, and 

 appear to contain refuse matter. After a time the creepmg 

 movement is again exchanged for the dancing. In all cultivations 

 of germinating spores, a number of the swarm-cells, after a snort 

 period of activity, withdraw the flagellum and become encysted 

 in a globular form, as the Tnicrocysts of Cienkowski. After being 

 dried and re- wetted, the contents bursts the membranous cyst-wall, 

 which remains as an empty hyaline sac, and emerges to resume 

 the swarm-cell form. If bacteria are introduced into a cultivation 

 of swarm-ceUs on the stage of the microscope, they are seen to 

 be laid hold of by the pseudopodia and drawn into the body 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 usually ceases after such ingestion, and 



that part of the swarm-cell 

 takes a rounded form. In 

 the course of an hour or two 

 the bacteria are assimilated, 

 and the digestive vacuoles dis- 

 appear. Unicellular algse and 

 inorganic matter are sometimes 

 taken in, which after a time are 

 again discharged. Both ingress 

 and egress are observed to 

 take place only at the posterior 

 end.* De Bary stated that 

 swarm- cells derive their sup- 

 port only from nutrient matter 

 in solution,t and it may be 

 that they are to some extent 

 nourished in this manner ; 



Fig. 2. — ^Amauroch^te atea Rost. 

 a to/. Successive stages 'in bipartitioii 



of 



swarm-cell, accompanied by the division of the but Considering the large num- 

 nucleiTS by karyokinesis. Magnified 1200 titnes. i p •ui" i. 



Drawn from stained preparations in Canada Der Ot specieS belonging tO 



^''^™- difEerent genera which have 



been observed to prey actively 

 on bacteria, it cannot be doubted that these form an important 

 part of their food. 



Bipartition of the swarm-cells is observed to begin in a few 

 hours after they leave the spore-membrane, and we may conclude 

 with de Bary that the process is frequently repeated, for it may 

 be seen constantly taking place for three or four consecutive days 

 in cultivations, during which time the numbers increase very 

 largely. The bipartition is preceded by the withdrawal of the 

 flagellum and the swarm-cell taking a spherical form. The 

 nucleus then divides by karyokinesis. The earliest stage which 

 I have observed is that of the nuclear-spindle with an equatorid,! 



* Lister, " On the Ingestion of Pood Material by the Swarm-Cells of 

 Ifyeetozoa." Linn. Soo. Jonrn. Bot., 1889, vol. xxv., p. 435. 

 -t De Bary, " Comp. Morph. and Biol. Fungi, Mycet.," etc., p. 452, 



