Laboratory Note. 
3 2 4 
LABORATORY NOTE. 
DEMONSTRATION OP CILIA IN LIVING VOLVOX. 
rnHE method described in the following note has been found 
useful and very satisfactory for the demonstration of moving 
cilia for class purposes, etc. 
Ulehla 1 in his work on cilia by dark-ground methods, found 
that of the members of the Volvocaceae which he tried, only Pandorina 
was suitable for observation ; the body of Volvox shone too brightly 
when thus illuminated, to permit of the study of the cilia. He 
apparently used young colonies. 
1 have found that although the cilia are very difficult to see 
when the colonies are freely swimming, yet they can be strikingly 
exhibited by the method. 
A Zeiss paraboloid is employed as a substage illuminator with 
an arc lamp, as source of light, to produce the dark-ground 
illumination ; the condenser must be very carefully centred. Fully 
developed colonies of Volvox are taken, placed on the slide in a 
little water and covered with an unsupported cover slip, which may 
be pressed very lightly with a needle. This serves to keep the 
colonies still and of course also flattens them to a certain extent. 
The motion of the cilia may be slowed down a little by this treat¬ 
ment, but is by no means stopped. A good focus may now be 
obtained on the edge of the colony. The cilia are then very clearly 
seen as bright lines against the dull ground, even with low powers, 
with which when the whole colony is in the field, a complete fringe 
of cilia is often evident around the colony. The manner of move¬ 
ment of the cilia appears to be much as in Pandorina , but it is not 
easy to study this with high powers. The very regular rhythm 
of the ciliary motion 2 as a whole is strikingly seen, the movement 
appearing to run round the contour of the colony in waves. 
The fact that the colony is held in position for any length of 
time, makes the object specially suitable for demonstration purposes. 
The activity ceases after a time, but other colonies on the same 
slide, which have not been subjected to the intense illumination, 
will often be found still to show the movement well. 
The Botany School, S. REGINALD PRICE. 
Cambridge. 
1 Ulehla, V. “ Ultramikroskopische Studien uber Geisselbewegung.” 
Biol. Centralbl., Bd. 31, 1911, p. 701. 
2 See, e.g., Pfeffer, “ Physiology of Plants,” Eng. Trans., Vol. Ill, p. 269. 
