LIFE-HISTORY 51 



the specimen has ingested several minute organisms and is 

 in the act of capturing another. 



But the main interest of Protomyxa lies in its very curious 

 and complicated life-history. After crawling over the Spirula 

 shells for a longer or shorter time it draws in its pseudopods, 

 comes to rest, and surrounds itself with a cyst (B, cy). The 

 composition of the cyst is not known, but it is apparently not 

 cellulose, since it is not coloured by iodine and sulphuric 

 acid (p. 28). 



Next, the encysted protoplasm undergoes multiple fission, 

 dividing into a number of spores (c) : soon the cyst bursts 

 and its contents emerge (D) as bodies which differ utterly in 

 appearance from the amoeboid form from which we started. 

 Each spore has in fact become a little ovoid body of an 

 orange colour, provided with a single flagellum (E, fl] by the 

 lashing of which it swims through the water after the manner 

 of a monad. 



It is convenient to have a name by which to distinguish these 

 flagellate bodies, just as we have special names for the young 

 of the higher animals such as tadpoles or kittens. From the 

 fact of their distinguishing character being the possession of a 

 flagellum they are called flagellultE ; the same name will be 

 applied to the flagellate young of various other organisms 

 which we shall study hereafter. 



After swimming about actively for a time each flagellula 

 settles down on some convenient substratum and undergoes 

 a remarkable change : its movements become sluggish, its 

 outline irregular, and its flagellum short and thick, until it 

 finally takes on the form of a little Amoeba (F). For this 

 stage also a name is required : it is not an Amoeba but an 

 amoeboid phase in the life-history of a totally different 

 organism : it is called an amotbida. 



The process just described may be taken as a practical 



