ROTIFERS. 
447 
The order Rhizota takes its name from its members being fixed when adult, and 
usually inhabiting a gelatinous tube. The foot is not retractile and ends in an 
adhesive disc or cup. In the flower-animalcules (Floscularia), which may be found 
everywhere in fresh 
water adhering to weeds, 
the edges of the wheel- 
disc are produced into 
distinct bristle-bearing 
lobes; but in the allied 
Melicerta there is no such 
production of the disc. 
The last order, 
Scirtopoda, comprises 
only the two genera 
Pedalion and Hexar- 
tlira, each of which is 
represented by a single 
species. The two re¬ 
semble each other and 
differ from 
rotifers in 
three pairs 
ending in a 
tuft of setae, 
is conical with a broad 
square - cut head, fur¬ 
nished with two wreaths 
of cilia and a pair of 
conspicuous eyes. In 
Hexarthra, which bears 
a strong superficial re¬ 
semblance to the Nawp- 
lius larva of some 
crustaceans, the three 
pairs of limbs spring 
from the ventral surface, 
the first pair being consideraoiy the largest and the third the shortest; but in 
Pedalion they are arranged round the body in pairs, one limb projecting from the 
middle of the back, another from the ventral middle line and two from each side, 
the ventral limb being the largest of the six. By means of these appendages 
the creatures are able to project themselves through the water in a series of 
jerks. Pedalion has been discovered in various parts of England, and Hexarthra, 
in brackish water in Egypt. The male of Pedalion is a veritable dwarf as 
compared with the female, the body and limbs being greatly reduced in size, and 
the latter merely represented by three stumps, each of which terminates in a pair 
of long bristles. 
all other 
possessing 
of limbs, 
fan-shaped 
The body 
flower-animalcule (magnified 200 times). 
