632 DESCEiPTioN OF [^Polygastricd. 



it may be consiclea'ecT as vl parasite, or ratlier an epiphjte. As they ai'c, 

 •wh.cn fully developed, attached mostly to some stationary object, 

 they afford many facilities to the microscopist for observation ; they 

 form a good object also for ascertaining the defining power of his 

 instrument, and his expertness in its management, as much of the 

 effect -will depend on the manner in which he manages the illumina- 

 tion. If this be not attended to, and the instrument has not 

 suffiiiient power and penetration, it will only exhibit two cilia 

 instead of a circular row ; indeed, this animalcule is described and 

 drawn in this manner by the old authors, an error which recent 

 improvements in the microscope have demonstrated. 



When in search of prey they stretch out the stem, and by means 

 of a vibratory motion communicated to the cilia they agitate the 

 water, and occasion a cm^ent towards them ; this brings along with 

 it the small particles of matter on which they feed. Should any 

 circumstance disturb the water, or a large animal approach them, they 

 instantly retract, bending the stem into a number of coils ; this 

 operation is performed so quickly, that the eye cannot detect it ; in 

 a few seconds, the creature may be observed slowly uncoiling the. 

 stem. These curious animalcules arc endowed with several methods 

 of propagation, the observation of which has thrown much light upon 

 this interesting subject, and enlarged oiu' views of the operations of 

 Nature in her minute productions : many creatm'cs, which Ave 

 formerly considered as belonging to distinct genera, are now ascer- 

 tained to be the same in different conditions. One method of 

 increase is probably from ova ; but of this we have no direct 

 evidence. Dr. E. considers that the spawn is ejected, as with Kol- 

 foda ; the first appearance of the young is like several little specks, 

 rather darker than the surrounding mass, and possessing a tremulous 

 motion; they are then not more than the 1- 12000th. of an inch in 

 diameter, and are clustered about the roots or stems of the old ones ; 

 they do not change their situation, and are probably connected to 

 the parent group by invisible filaments ; they soon increase in size, 

 when delicate stems may be perceived, as may also a current in the 

 water towards the bell, indicating the presence of cilia. At this 

 stage of their growth, they have been considered as a distinct species 



