S YSTEMA TIC SUR VE Y. 107 



have a rind and no motile processes or outflowings, may 

 be compared to degenerate muscle cells, or to mature ova, 

 or to "encysted" passive cells in higher animals. 



This comparison has been worked out by Professor Geddes, who also 

 points out that the classification represents the three physiological 

 possibilities (a) the amoeboid units, neither very active nor very passive, 

 form a median compromise ; (b} the ciliated Infusorians, which are 

 usually smaller, show the result of a relative predominance of expendi- 

 ture ; (c] the encysted Gregarines represent an extreme of sluggish 

 passivity. 



But, as Geddes and others have shown, the cells of a higher animal 

 often pass from one phase to another, the young amoeboid ovum 

 accumulating yolk becomes encysted, the ciliated cells of the windpipe 

 may, to our discomfort, sink into amoeboid forms. The same is true of 

 the Protozoa ; thus in various conditions the ciliated or flagellate unit 

 may become encysted or amceboid, while in some of the simplest forms, 

 such as Protomyxa, there is a " cell-cycle " in which all the phases occur 

 in one life history. 



SYSTEMATIC SURVEY 



A. Primitive forms. Under this heading may be included two 

 classes : (i) the Proteornyxa, primitive, insufficiently known forms often 

 without a nucleus, though nuclear material may be present in the form 

 of scattered granules (chromidia), and (2) the Mycetozoa, organisms 

 with somewhat complex fructifications, often classed as plants allied 



FIG. 48. Diagram of Protomyxa auranttaca. After Haeckel. 



x. Encysted ; 2. Dividing into spores ; 3. Escape of spores, at first 

 flagellate, then amoeboid ; 4. Plasmodium, formed from fusion of 

 small amoebae. 



to Fungi. As examples of the Proteornyxa, we have the interesting 

 Protomyxa in four phases : (a) encysted and breaking up into spores, 

 which (b} are briefly flagellate, (c) sink into amoeboid forms, and (d) 

 flow together into a composite " plasmodium " ; Vampyrella, parasitic 

 on fresh- water Algse ; and many others. 



The Mycetozoa are well illustrated by Fuligo or AZtkalium septicum, 

 "flowers of tan," found in summer as a large plasmodium on the bark 

 of the tan-yard. The coated spores are formed in little capsules which 

 rise from the surface of the plasmodium. The spores may be first 

 flagellate, then amoeboid, or amoeboid from the first ; the characteristic 

 plasmodium is formed by the fusion of the amoebae. 



