DIPS IXTO MY AQUARIUM. 257 



Protozoa, whereas Rotifers, as previously explained, are grouped 

 amongst the Sco/ecida, or lowly worms. 



The only movement Vorticella seems capable of, apart from 

 ciliary vibration, is a curious action of the stalk. Every few 

 moments you can see one of the slender stalks suddenly twist 

 itself into a spiral or corkscrew pattern, thus bringing the vase 

 close to the plant on which it lives, but very soon the stem 

 lengthens out again, and the cilia once more resume operations. 



Taking now a higher power it is possible to discern that the 

 cilia are set around the inner rim of the bell, and that when in 

 full activity they produce a couple of tiny round vortices outside 

 the organisms ; hence the name Vorticella or vortex-making 

 animalcule. You can also distinguish the mouth, oesophagus, and 

 orifice for the rejection of undigested food. No intestinal canal 

 has been discovered, but the food on leaving the oesophagus goes 

 to various parts of the sarcode and a temporary stomach may be 

 set up 'anywhere. With oblique or dark-ground illumination some 

 other interesting facts can be made out. The vases are not open 

 at the top, as might at first be supposed, but they possess a 

 retractile cover, on which the cilia rest. The stalks, too, are 

 hollow or tubular, and are probably moved by some sort of 

 rudimentary muscular structure. Sometimes a nucleus of gra- 

 nular structure is observed, which is thought to be an ovary, 

 while there is also a contractile vesicle which may be concerned in 

 respiration. These are usually made visible by adding a minute 

 quantity of pigment, carmine, or indigo, to the water in the cell in 

 which they are being exhibited. 



Several of the individuals of our colony are gradually assuming 

 pronounced differences of shape, even while we are observing 

 them. Some leave their stalks and enjoy a sort of independence, 

 while others tuck in their cilia, which are absorbed into the 

 sarcode (^) ; grow uneven i^B) ; and separate into two distinct 

 vases ( C) ; which develop a new set of cilia (Z>, E) ; the young 

 individual at length breaking away {F) ; and after a brief enjoy- 

 ment of wild liberty rooting itself on the plant {G) ; thus founding 

 another colony. It would require several hours of patient and 

 continuous watching to trace the same individual through all these 

 transformations, but it is not very difficult to discern all these 



Journal of Microscopy and Natural Science. 



New Series. Vol. III. 1890. t 



