412 ELEMENTARY BIOLOGY. [CHAP. 



3. Take a drop of fluid from a turbid hay infusion — 

 and examine it, using the highest power you have; 

 in it will be found multitudes of 



Moving Bacteria. Note their — 



a. Form; elliptic or rodlike — sometimes forming 

 short (2 — 8) jointed rows. 



b. Size; breadth, very small but pretty constant; 

 length, varying, but several times greater than 

 their breadth : measure. 



c. Structure; an outer more transparent layer en- 

 veloping less transparent matter: in the com- 

 pound forms ' the envelope appears only where 

 two joints come in contact, so that the rod looks 

 as if made up of alternating transparent. and more 

 opaque substances. 



d. Movements; some vital, and some purely physical 

 (Brownian). The former various but progressive : 

 the latter a rotatory movement round a stationary 

 centre; study it in a drop of boiled infusion in 

 which the Bacteria are all dead. 



4. Treat with iodine — only the more opaque parts 



stain; probably then we have to do with proto- 

 plasm, enveloped in nonprotoplasmic matter. 



5. Resting Bacteria. {Zooglwa-stage.) 



a. Examine the scum from the surface of a hay 

 infusion; it exhibits myriads of motionless Bac- 

 teria, embedded in gelatinous material. 



b. Treat with iodine ; the Bacteria stain as before : 

 the gelatinous uniting material remains un- 

 stained. 



