THE SIMPLER ORGANISMS 77 



Stentor. — This is a large protozoan that is often found 

 adherent to submerged twigs and leaves, and that is usually 

 obtained by placing the trash from a pond in jars of water 

 and letting it stand a few hours. The stentors, large 

 enough to be seen w^th the unaided eye, and to be cer- 

 tainly recognized with a pocket lens, w^ill be found extended 

 in the form of a trumpet, the narrow basal end attached to 

 the twigs, etc., or suspended beneath the surface film. If a 

 twig bearing stentors attached be transferred to a slide, 

 covered, and allowed abundance of room and plenty of 

 water beneath the cover, the stentors will soon be ready for 

 observation, and for the work of the following outline: 



1. Make a preliminary survey of the contents of the 

 mount, finding: 



a) Stentors extended and trumpet shaped (whence their 

 name), and attached by their slender bases to some 

 support. 



b) Others contracted into globular or club-shaped 

 form. If possessing a gelatinous cup-shaped 

 receptacle about theii' bases of the sort known as a 

 lorica (fig. 53 C, ^), these will be more or less with- 

 drawn into it. 



c) Others detached, more or less contracted, and lying 

 free or swimming about in the water with something 

 of the spiral rolling motion of Paramoecium. These 

 may have been detached in mounting; however, 

 Stentor may voluntarily make a change of base. 



2. Find a little group that may be brought into the field 

 with the lowest power of the microscope, and take time to 

 study their actions: 



a) While watching a fully extended animal through 

 the microscope, tap or jar the slide sharply and see 

 it contract : continue watching until it is again fully 

 extended. 



