MORPHOLOGY 73 



somes and food vacuoles of Amoeba and Paramecium, Horning 

 suggested that the chondriosomes are the seat of enzyme activity 

 and it is even probable that they actually give up their own sub- 

 stance for this purpose. The view that the chondriosomes may 

 have something to do with the cell-respiration expressed by 

 Kingsbury was further elaborated by Joyet-Lavergne through 

 his studies on certain Sporozoa. That the chondriosomes are ac- 

 tively concerned with the development of the gametes of the 

 Metazoa is well known. Zweibaum's observation, showing an in- 

 crease in the amount of fatty acid in Paramecium just prior to 

 conjugation, appears to suggest this function. On the other hand, 

 Calkins found that in Uroleptus, the chondriosomes became 

 abundant in exconjugants, due to transformation of the macro- 

 nuclear material into the chondriosomes. It may be stated that 

 the chondriosomes appear to be associated with the formation of 

 enzymes which participate actively in the processes of catalysis 

 or synthesis in the protozoan body. The author agrees with 

 McBride and Hewer who wrote: "it is a remarkable thing that so 

 Httle is known positively about one of the 'best known' proto- 

 plasmic inclusions." 



The contractile and other vacuoles 



The majority of Protozoa possess one or more vacuoles known 

 as pulsating or contractile vacuoles. They occur regularly in all 

 freshwater inhabiting Sarcodina and Mastigophora, and in Cilio- 

 phora regardless of habitat. In the Sporozoa, which are all para- 

 sitic, and the Sarcodina and Mastigophora, which live either in 

 salt water or in the body of other animals, there is no contractile 

 vacuole. 



In various species of free-living amoebae, the contractile vacu- 

 ole is formed by accumulation of water in one or more droplets 

 which finally fuse into one. It enlarges itself continuously until 

 it reaches a maximum size (diastole) and suddenly bursts through 

 the thin cytoplasmic layer above it (systole), discharging its con- 

 tents to outside. The location of the vacuole is not definite in such 

 forms and, therefore, it moves about with the cytoplasmic move- 

 ments; and, as a rule, it is confined to the temporary posterior 

 region of the body. Although almost spherical in form, it may oc- 

 casionally be irregular in shape, as in Amoeba striata (Fig. 140, 

 /). In many testaceans and heliozoans, the contractile vacuoles 



