THE CILIATE INFUSORIA. 37 
opens, allows the rejected matter to pass out, and then 
eloses over, leaving no trace of an outlet. This and other 
Infusoria seem, then, to have a definite digestive tract, hol- 
lowed out of the parenchyma of the body. 
‘The system,’’ says Clark, ‘‘ which-is analogous to the 
blood-circulation of the higher animals, is‘ represented in 
Paramecium by two contractile vesicles (cv, cv', 1, I, II), 
both of which have a degree. of: complication which, : ‘per- 
haps, exceeds that of any other similar organ” in these ani- 
mals. When fully expanded they appear round, as at cv; 
but when contracted they appear, observes Clark, as “‘ fine 
radiating streaks, and as the main portion lessens they grad- 
ually broaden and swell until the former is emptied and 
nearly. invisible, and 
they are extended 
over half the length 
of the body. In this 
condition they might 
be compared to the 
arterial vessels of the J 
more elevated classes #f 
of animals, but they # 
would at the sume , Pech Peceeet seine ugly mtr 
time represent the the original one; f, the two in a contracted state. — 
‘ h After Cox. 
veins, since they 
serve at the next moment to return the fluid to the main 
reservoir again, which is effected in this very remarkable 
way.’’ The contents of these vesicles is a clear fluid. 
The reproductive organ in Paramecium isa small tube 
(n), only seen at the reproductive period when the eggs (m) 
are fully grown. Clark says that the eggs are arranged in 
it ‘in a single line, one after the other, at varying dis- 
tances.’’ It usually lies in the midst of the body, and ex- 
tends from one half to two thirds of the length of the ani- 
mal. The eggs pass out from the so-called ovary through 
an aperture near the mouth. Lasso-cells like those in the 
jelly-fishes are said by Bitschli to exist in an infusorian 
named by him Polykrikos. 
In the trumpet animaloule (Fig. 25, Stentor polymor- 
