310 JULIAN 8. HUXLEY 
together with a thickening of its walls. The collars are usually 
retracted. (See figs. 10, a, and 10, b.) 
This sensitiveness to mechanical stimuli is shown by many 
other tissues in culture (cf. Holmes, 6). 
Exposure to very dilute solution of mercuric chloride in 
( n oe n 
500,000 2,000,000 
the collar and then, gradually, of the flagellum, together with 
slowing of the flagellar beat. The effect is proportional to the 
strength of the solution. This retraction of the flagellum is a 
remarkable phenomenon, and the short stumps of the flagella 
still beating provide a curious spectacle. 
A record of an experiment is appended. 
gea-water ) causes retraction, first of 
RECORD OF EXPERIMENT. 
Five or six collar-cell blow-outs in each solution (100 ¢.c. each). 
A. Control, Collarsand flagella remained normal for twenty-four hours, 
n , 
1,500,000 A&C». 
l hr. 25m. Two masses with short collars. Three masses with 
very short or no collars, and sharp smooth outline of epithelium, 
all with fair to good flagellar movement, 
2hrs. 10m. None with more than very short collars. Some 
with short flagella. These beating faster than unretracted 
flagella of other masses. Smooth outline still visible. 
19hrs. No collars. Only two with flagella (moderate length), 
two with slight cell-disintegration. 
n Y 
C. 750.000 HgCl,. 
lhr. 10m. One mass with short collars in most cells, one mass 
with vestigial collars, remainder without collars, Flagellar 
action moderate, one with shortened flagella. Blow-outs 
shrunken in all but one. Some cell-disintegration. 
2hrs. No collars. Flagellar action slow and spasmodic. 
1S hrs. No flagella. All masses with much disintegration into 
separate cells. 
n 
D- 900,000 F&C»: 
lhr. No collars. Flagellar action very slow or nil.  Flagella 
absent or normal length, Two blow-outs still present. 
