THE MYCETOZOA 



which thus enters the swarm -cell or zoospore stage swims free 

 in the water with a peculiar dancing movement produced by the 

 lashing of the flagellum. In this movement it rotates about its own 

 axis, and also moves as though over the surface of a cone, the apex of 

 which is situated at the posterior end of the zoospore (de Bary). 

 It is of an elongated pyriform shape, the narrow (" anterior ") end 

 being continued into the flagellum, which is about half to two- 

 thirds the length of the body. The thicker (" posterior ") end may 

 be evenly rounded, and is then curled somewhat to the side, but 

 is often extended in short pointed pseudopodia (Fig. 2, ). The 

 protoplasm of the anterior part is hyaline, and a layer of hyaline 

 protoplasm invests the rest of the body, the interior of which is 

 granular. The nucleus, with its contained nucleolus, lies in front, 

 At the base of the flagellum, and the contractile vacuole at the 

 posterior end. Non-contractile vacuoles (some of which at least 

 may be food- vacuoles) are also present in the granular protoplasm. 

 The particles of the latter exhibit a change of position within the 

 body, which in the large swarm-cells of Amaurocliaete atra recalls the 

 streaming movement characteristic of the plasmodia of the later stage. 



Instead of swimming free, the swarm -cells may temporarily 

 assume an attached creeping mode of progression, in which the 

 body is elongated, and the flagellum, ex- 

 tended in front, turns from side to side 

 with movements which appear to be ex- 

 ploratory in purpose. Sometimes the body 

 is contracted and sends out pseudopodia 

 from all parts of the periphery (Fig. 4, c). 



Bacteria abound in the wet places among 

 decaying vegetable matter, in which the 

 spores hatch. These are captured by the 

 zoospores by means of the pseudopodia ex- 

 tended from their posterior ends and drawn 

 into the body, where they are digested in 

 vacuoles (Fig. 2) (15). De Bary, to whom 

 this mode of obtaining food by the zoospores 

 was unknown, states (8, p. 452) that their 

 nourishment is exclusively saprophytic at 

 this stage. 

 it may be 

 appears very probable that it is both holozoic and saprophytic. 



The swarm -cells multiply by division. In this process the 

 flagellum is withdrawn, the contractile vacuole disappears, and the 

 body assumes a rounded form. The nucleus, passing to the centre, 

 divides by karyokinesis (Fig. 3), and as the daughter nuclei resulting 

 from this division separate the protoplasm becomes constricted, and 

 -division occurs in a plane transverse to the axis of division of the 



Zoospore of Stcmnnitis fusca, 

 showing successive stages in 

 the ingestion of a bacillus, 

 x 800. In , it is captured by 

 one of the pseudopodia at the 

 hind end ; in c, it is enclosed 

 in a digestive vacnole. Another 

 bacillus is contained in an 

 (After A. 



It is impossible to deny that Anterior vacuole. 



. . J . Lister, 15.) 



in part saprophytic, and it 



