14 GEORGE BIDDER. 
apochromatic 2:0 mm. objective of 1°40 aperture, ocular 8. 
With this power the beaded appearance from above is conspi- 
cuous in all cells of good sections strongly stained with hema- 
toxylin. See subjoined woodcut, 0. 
a, 6, Collar-cells over-stained in bulk (Series D), showing in a (profile) inter- 
stitial substance, and in J (from above) iris membrane. Same slide as 
fig. 15, e, Plate 2. 
c. From Series A, stained borax carmine and hematoxylin, extracted with 
acid, focussed on flagellum to show connection with nucleus and per- 
foration of nuclear membrane. 
d. Series D, cleared with olive oil, stained on slide with hematoxylin, extracted 
with acid. Showing pear-shaped nucleus and perforation of iris. 
From drawings made with Zeiss apochromatic immersion, 2 mm., ap. 1°40, 
oc. 8. ; 
The “ beads” remain sharply defined while focussing from 
top to bottom of the collar, each bead being about '25 « in 
diameter, and the less stained interspace between them about 
‘15 4. The number seems to be fairly constant; though I 
never succeeded in counting exactly, it was in no collar esti- 
mated at less than twenty or more than six-and-thirty for S. 
compressum. The collar is, in fact, composed of a series of 
twenty or thirty parallel rods, or non-vibratile cilia, staining 
with hematoxylin, though less darkly than the flagellum, and 
united by a thinner film of non-staining substance. The 
