THE VILIATE INFUSORIA. 



37 



opens, allows the rejected matter to pass out, and then 

 •closes 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 

 Tjlood-circulation of the higher animals, is represented in 

 Paramecium by two contractile vesicles {cv, cv^, i, ii, iii), 

 toth of which have a degree of complication which, per- 

 haps, exceeds that of any other similar organ" in tliese ani- 

 mals. When f ally expanded they appear round, as at c v ; 

 but when contracted they appear, observes Clark, as " fine 

 radiating streaks, and as the main portion lessens they gi'ad- 

 Tially broaden and swell until the former is emptied and 

 Tiearly invisible, and 

 iihey are extended a h 



■over half the length 

 of the body. In this 

 condition they might 

 he compared to the 

 -arterial vessels of the 

 more elevated classes 

 of animals, but they 

 would at the same 

 i;ime represent the 

 Teins, since they 

 .serve at the next moment to return the fluid to the main 

 j-eservoir again, which is effected in this very remarkable 

 "way." The contents of these vesicles is a clear fluid. 



The reproductive organ in Paramecium is a small tube 

 {n), only seen at the reproductive period when the eggs (ji) 

 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 Biitschli to exist in an infusorian 

 Jiamed by him Polykrikos. 



In the trumpet animalcule (Fig. 26, Stentor polymor- 



Fig. 26 — Process of fission in Sienior polyTUorphis. 

 b, a new Stentor budding out; e, ready to separate from 

 the original one; /, the two in a contracted state.— 

 After Cox. 



