U-n-iou of the Advent tend [< > accumulate at the surface in higher 

 concentration than in the interim' and may there form coherent 

 membranes or films. The formation of cell membranes and similar 

 structures in organism.- has been thus e\])lained. 



II. Fl \RCE ( )!' FA AI'oKATK )X. 



i iii. Fill a porous cup with water and place in a beaker <>t 

 water for in or 15 minute-. Then insert a rubber -topper through 

 which pa-ses a gla-s tube into the porous cup, and till the whole 

 apparalu- with water. Then place the free end of the water-tilled 

 tube under mercury in a glas- vc-sel and clam]) in an upright position. 

 lias the mercury begun to rise in the tube by the end of the 

 laboratory period? Why? Leave till next da}'. 



I. AM< >FIU )ll) M( >YK.MKXT. 



\><2. The preceding e.\])eriments have brought out various princi- 

 ples bearing on surface teiisii n. The student should now ende:i\ or 

 to apply them to the study of movement in the living organism, 

 amoeba, whose mode of locomotion is commonly attributed to 

 change- in it- surface tension. The experiments and observations 

 -hould be devi.-ed by the student and conducted in the spirit of re- 

 -earch. in an endeavor to prove or disprove the surface-tensi n 

 theory of movement. First make sure of the facts by a careful 

 study of the Amoeba from above. Determine which species of 

 Amoeba you are observing from I 'late I of I'onn's "Protozoa". 



The following are suggested as points worthy of notice: 



Can a pseudopodium be thrust out freely into the water, or mu.-i 

 it be in contact with the substratum? 



( 'bserve a- exactlv a- possible the current- ot protoplasm in the 

 amoeba and the currents in the water about the amoeba. The 

 latter, if any. may be oh-erved by india ink granule- in the water. 



I )o particles of soot or debri- clinging to the surface < t amoeba 

 move completely around the animal as if it were a bag rolling 

 ab< int < '11 the slide ? 



I )oes the amoeba move forward in jerks or gradually? 



\\hat i- the character of the movement when viewed I mm the 

 side.' I -e the -peciallv prepared -lide for this purpose. Study care- 

 lnll\ ; manv of the phenomena connected with the movement become 

 clear when examined from the -ide. I )oe- the amoeba adhere to the 

 substratum? * an it move up a vertical -urface? 



40 



