PROTOZOA 25 
Vertebrates and Arthropods. Huglena viridis often exists in 
such numbers as to turn the water green, and a species of 
Haematococcus is responsible for the red snow of the Arctic 
regions. Many of them, such as Polytoma, thrive in putrid 
Fie. 19.—Proterospongia Haeckeli, Sav. Kent. x 800. 
1. Nucleus. 6. Other individuals undergoing 
2. Contractile vacuole. fission. 
3. Collar. 7. Individual with collar contracted. 
4. Flagellum. 8. Individual divided up into number 
5, Amoeboid individual sunk in sup- of spores (microgonidia). 
We} 
porting jelly. . Jelly-like supporting matrix. 
liquids, such as the water of macerating tubs, and these forms 
are mostly saprophytic. 
Some of the lower forms are apt to withdraw their flagellum 
and become amoeboid (Cilzophrys) ; in others (Cercomonas), the 
posterior end of the body is very apt to throw out pseudopodia, 
and the young of many species exhibit amoeboid movements. 
These facts support the view that the Flagellata are derived 
from the Gymnomyxa; and indeed there are certain forms 
which might equally well find a place in the class Proteo- 
myxa, 
Ciass II. Rhynchoflagellata. 
This class contains but one or two genera. One of them, 
Noctiluca, attains a large size: y!; of an inch in diameter. It is 
