16 



PROTOZOA. 



The reproduction is always effected by spore-formation. The 

 spores are either contained within fruit-like cysts the Sporangia 

 (Endosporece), which are either simple (spore fruits) (Fig. 11) or 

 combined into an cethalium (fruit-cake) of a cushion-like shape 

 consisting of numerous convoluted sporangia (Fig. 12); or they are 

 not contained in a cyst, but are produced upon the surface of 

 upgrowths of the plasmodium the sporophore (Exosporece). 

 In the latter case the spores divide, after issuing as amoeboid 

 organisms, by three successive bipartitions into eight cells, 

 which soon obtain flagella and separate ; they are comparable to the 

 just-hatched spores of the Endosporece. The spores are always 

 enclosed in a coat of a cellulose-like material and possess a single 

 nucleus. They are contained as a rule in the meshes of a network of 

 supporting fibres the capillitium which is formed within the 



FIG. 11. Physamm nutans (from Lister), 

 a, two sporangia magnified nine times ; 

 ?>, capillitium threads, with lime-knots 

 attached to a fragment of the sporangium- 

 wall, x 110. 



FIG. 12. Fuligo septica, a, Aethalium, one 

 third natural size ; b, capillitium threads 

 with lime-knots and two spores, x 120. 



sporangial cyst by the spore-protoplasm. The division into spores is 

 in the Endosporece preceded by a single division of the nuclei of the 

 sporeplasm by karyokinesis. * On the germination of the spore 

 the spore coat bursts and the contents issues as an amoeboid 

 organism which soon protrudes one flagellum. (Fig. 13.) The 

 swarm-cells so formed swim by their flagellum, ingest solid food 

 by their pseudopodia (at the non-flagellate end) and undergo 

 frequent bipartition. They may also withdraw the flagellum and 

 encyst (microcysts), but this is only temporary : they emerge and 

 re-assume the swarm-cell form. After a time the flagellum is 

 withdrawn and they creep about in an amoeboid manner, and 

 ultimately several of them fuse together to form the multinucleated 

 plasmodium. (Fig. 14.) 



* The nuclei of the plasmodium sometimes multiply simultaneously by 

 karyokinesis, though it is highly probable that simple division occurs as well. 



