$ 



MYCETOZOA 



usually ceases for a time after such ingestion, and the hinder 

 end of the swarm-cell takes a rounded form. In the course 

 of an hour or two the bacteria are assimilated, and the digestive 

 vacuoles disappear. Unicellular algae and inorganic matter 

 are sometimes taken in, which are subsequently discharged. 

 Both ingress and egress are observed to take place only at the 

 posterior end.* De Bary stated that swarm-cells derive 

 their support only from nutrient matter in solutionf , and it may 

 be that they are to some extent nourished in this manner ; but 

 considering the large number of species belonging to different 

 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 a few 

 hours after they leave the spore-case, and is several times 

 repeated in the course of the three, or four succeeding days. 

 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 swarm- 

 cell becomes ellipsoid and 

 later a constriction ap- 

 pears in the middle. As 

 bipartition proceeds .the 

 nuclear plate divides and 

 the two halves separate, 

 the connecting achromatic 

 fibres being discernible. 

 The daughter-nuclei at 

 Fig. 3.— didymium difforme Duby. length retreat to the op- 

 Young Plasmodium, with converging amoe- posite poles of the SWarm- 

 boid swarm-cells. A number of microcysts (m) np ii whir>h in ihmif a 

 were present in this preparation, one of which CBU ' "'J^"- *" «*uuuu <* 

 is being digested in a vacuole (v). An empty quarter of an hour from 

 spore-shell is shown at s. . , ■■ - , , 



Magnified 470 times. the beginning of the pro- 



cess of constriction is com- 

 pletely divided (fig. 2). A flagellum is in a short time produced 

 by each daughter-cell, which then assumes the original form 

 of the parent. Jahn has shown that the bell-shaped tract 

 crowning the nucleus is formed again after mitosis from the 

 spindle fibres of the dividing nucleus, and that the flagellum 

 is produced from its apex (I.e., p. 89). 



After dividing in the manner described, through a period 

 of uncertain duration, the swarm-cells withdraw the flagellum, 



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

 .in Journ. Linn. Soc. (Bot.) XXV. 435 (1889). 



t De Bary, " Comp. Morph. and Biol. Fungi, Mycetozoa, etc.," 452. 



