THE PROTOZOA 147 



The treponema is a spiral, curved organism from 5 to 15 

 microns in length, showing active movements in fresh specimens. 



Syphillis is one of the most serious and far-reaching of all dis- 

 eases, in fact so far-reaching that one of the world's greatest diagnos- 

 ticians has said that if one could know every ramification of this dis- 

 ease he would know nearly all there was to medicine. Doubtful if 

 curable. 



Though all symptoms are gone, the disease may appear again. 



In fact, in prisons, where there was little likelihood of a second 

 infection, symptoms have appeared ten years after a supposed cure. 



THE PROTOZOA, SUMMARY OF IMPORTANT FACTS 



(Table Modified from R. Hertwig and R. W. Hegner.) 



1. The Protozoa are unicellular organisms without true organs or 

 true tissues. 



2. All vital processes are accomplished by the protoplasm (sar- 

 code), digestion directly by its substance, locomotion and the taking of 

 food by means of protoplasmic processes (pseudopodia), or by appen- 

 dages (cilia and flagella). 



3. Excretion takes place by special accumulation of fluid, the con- 

 tractile vacuoles. 



4. Reproduction is by budding or by fission. Conjugation has 

 been witnessed in many, and possibly occurs in all. True conjugation 

 is a process of fertilization (caryogamy), in contrast to fusion of plasma 

 (plasmogamy). 



5. Protozoa are aquatic, a few living in moist earth ; they can only 

 exist in dry air in the encysted condition, surrounded by a capsule which 

 prevents desiccation. 



6. Since encysted Protozoa are easily carried by the wind, the oc- 

 currence of these animals in water which originally contained none is 

 easily explained. 



7. The mode of locomotion serves largely as a basis for division 

 of the Protozoa into the classes Rhizopoda, Mastigophora, Infusoria 

 and Sporozoa. 



8. The Rhizopoda are subdivided into the following orders : 

 Lobosa, Heliozoa, Radiolaria, and Foraminifera. 



9. The Rhizopoda have changeable protoplasmic processes, the 

 pseudopodia. 



10. Order 1. Lobosa ( ). Rhizopoda with 

 fmgerlike (lobose) pseudopodia. Most of the Lobosa occur in fresh 

 water, a few in moist earth, and some are parasites. 



Examples: Amoeba, Arcella and Difflugia. (Fig. 63 .) 



Arcella ( ) is common in the ooze on the bot- 



toms of fresh-water ponds and ditches. It has a dome-shaped brownish 

 shell of chitin which it secretes. The lobose pseudopodia protrude from 



