3542 



THE LOWEST ANIMALS 



is like that of a wineglass, is provided at the rim with an incomplete circlet of cilia, 

 one end of which passes down into the mouth funnel at the margin (r) of the disc; 

 the stalk contains a contractile band (m) which produces a rapid jerking motion by 

 throwing the stem into coils; in the body mass lie the nucleus () and contractile 

 vacuole (z>). Reproduction takes place by transverse division into two. Ehrenberg 

 observed twelve individuals to originate from one within twenty- four hours, so that, 

 calculating on this basis, one million individuals would be produced within twenty 

 days. The common-branched bell animalcule {Carchesiutn} divides more rapidly, 

 namely, once in an hour; each again being soon ready for division, so that one 



thousand could arise in ten 

 hours, and a million in twenty 

 hours; but, as a matter of 

 fact, only two hundred have 

 actually been observed to 

 have been formed in one day, 

 owing to the intervals be- 

 tween successive divisions be- 

 coming longer. The vigor 

 of the exhausted stock be- 

 comes rejuvenated, however, 

 by the fusion or conjugation 

 of two individuals into one. 

 The nodding bell animal- 

 cule (Epistylis*) forms little 

 branching colonies growing 

 on Conferva in stagnant 

 water. When the animal is 

 disturbed, the heads droop 

 down toward the stalks. One 

 of the forms most frequently 

 met with is Carchesium, 

 whose tiny branched tree- 

 like colonies resemble molds; 

 but a few moments' inspec- 

 tion will undeceive the ob- 



MARINK ANIMALCULE, Atineta (magnified 600 diameters). . server > Ior the little white 



globular stalked heads will 



be seen to be drawn down toward the base of the colony with a rapid jerking 

 movement. 



The trumpet animalcule {Stentor) is of comparatively large size, being about 

 one-twenty-fifth of an inch in length when extended. It is usually to be found 

 fixed by its pointed end on the under side of duckweed. Its form continually 

 alters from a small knob when contracted, to a trumpet-shaped body when ex- 

 tended; and when in motion its shape continually changes, being in turn ovoid, 

 pyriform, or even spherical. The surface is corrugated and covered with rows of 



