ii PHYLUM PROTOZOA 03 



(c. vac.). The flagellulse move freely and ingest Bacilli (D, 1>.) ; then, after a 

 time, they become irregular in outline, draw in the flagellum, and become 

 amoeboid (E). The amcebulte thus formed congregate in considerable numbers 

 and fuse with one another (F), the final result being the production of the 

 great amoeboid mass (G) with which we started. There is no fusion of the 

 nuclei of the amcebulse. Thus Didymium in its active condition is aplasmodium, 

 i.e. a body formed by the concrescence of amcebulse. 



2. GENERAL REMARKS ON THE MYCETOZOA. 



Speaking generally, the Mycetozoa differ from all other Protozoa in their 

 terrestrial habit. They are neither aquatic, like most members of the phylum, 

 nor parasitic, like many other forms, but live habitually a sub-aerial life on 

 decaying organic matter. Thej 7 are also remarkable for their close resemblance 

 in the structure of the sporangia and spores to certain Funyi, a group of parasitic 

 or saprophytic plants in which they are often included, most works on Botany 

 having a section on the Myxomycetex or " Slime-fungi," as these organisms are 

 then called. They are placed among animals on account of the structure and 

 physiology of the flagellate, amoeboid, and plasmodial phases which exhibit 

 automatic movements and ingest solid food. On the other hand, the Mycetozoa 

 are sometimes included among the Rhizopoda, a course which their very peculiar 

 reproductive processes appears to render inadvisable. 



An interesting organism, called Protomyxa, probably belongs to this group. In 

 its plasmodial phase it consists of orange-coloured masses of protoplasm, about 

 1 mm. in diameter, which crawl over sea-shells by means of their long, branched 

 pseudopods, and ingest living prey. No nuclei are known. The protoplasm 

 becomes encysted and breaks up into naked spores, which escape from the cyst 

 as flagellulte, but soon become amoeboid and fuse to form the plasmodium. 



CLASS III. MASTIGOPHORA. 



1. EXAMPLE OF THE CLASS finglena mridis. 



Euglena (Fig. 46) is a flagellate organism commonly found in 

 the water of ponds and puddles, to which it imparts a green colour. 

 The body (E, H) is spindle-shaped, and has at the blunt anterior 

 end a depression, the gullet (F, ccs.}, from the inner surface of which 

 springs a single long flagellum (_/?.). According to recent observa- 

 tions the flagellum is not a simple thread, but is beset with delicate 

 cilium-like processes. The organism is propelled through the 

 water by the lashing movements of the flagellum, which is always 

 directed forwards ; it can also perform slow worm-like movements 

 of contraction and expansion (A D), but anything like the free 

 pseudopodial movements which characterise the Rhizopoda is 

 precluded by the presence of a very thin skin or cuticle which 

 invests the body. There is a nucleus (nu.) near the centre of the 

 body, and at the anterior end a contractile vacuole (H, c. vac.}, 

 leading into a large non-contractile space or reservoir (r.) which 

 discharges into the gullet. 



The greater part of the body is coloured green by the charac- 

 teristic vegetable pigment, chlorophyll, and contains grains of 



