288 PRACTICAL DIRFXTIONS chap, hi 



there are no trichocysts. Moreover, in the stalk (into which the 

 medulla does not extend) the deeper layer of the cortex gives rise to a 

 central conlraclUc axial fibre, liy means of which the stalk cSTi contract 

 spirally. 



6. The medulla, which circulates and contains food-vacuoles, as in 

 Paramoicium. The single spherical contractik I'acuok is also situated 

 in it, as well as an elongated and curved vicgnniiclcus and a small 

 luuronitckus [x\uV easy to distinguish). Sketch. 



7. Make preparations as directed under Paramoecium. Sketch. 



S. Took out for specimens undergoing y?.r.«'fl//, noting the different 

 stages, and the second, ahoral ring of cilia on otw of the daughter 

 individuals, which e\entua]ly becomes detached. Note these free 

 swiiiuniui^ forfus, and also search fur eoitjugaling individuals — a small 

 free \'ortice!la uniting with a large stationary one. Sketch. 



Carchesium or Epistylis. — Vou will very likely find specimens of 

 one of these, < t of an allied genus, amongst the \'orticelk\-. Ncjte 

 that several individual zooids are borne upon a branched stalk, together 

 forming a colony. 



