264 EDWARD A. MINCHIN. 
distinctly, as described by Dendy.’ The flagellum is usually 
about twice the height of the cell, or more. In the cell in fig. 
16, which I had under continuous observation for a Jong time, 
TI noticed that the flagellum made a somewhat slow stroke to 
the right, followed immediately by a quick stroke to the left, 
after which there was a pause, and then the two strokes were 
repeated, and so on. Similar rhythmic pulsations were ob- 
served in other cells, and doubtless have to do with causing a 
current in a definite direction. I observed, also, that when a 
foreign body came into contact with the end of the flagellum 
so as to hinder its movements, it stimulated it to greater 
activity, and caused it to lash about violently so as to become 
almost invisible, until the foreign body was thrust away, or the 
cell itself removed from it. When the flagellum was in full 
swing it appeared thicker at the base than at the tip. But 
during its pauses it was easy to see that this apparent disparity 
in thickness was an optical delusion (owing, presumably, to 
the tip moving more quickly than the base), and the flagellum 
was really of precisely the same thickness throughout. Similar 
observations have been made by Clark and Biitschli® on the 
flagella of Flagellata, and these authors have shown that in 
many species the flagellum, though depicted by earlier writers 
as tapering towards the tip, was really quite cylindrical. Von 
Lendenfeld, in his ‘Monograph of the Horny Sponges’ 
(p. 777), draws the flagellum of Spongelia distans tapering 
towards the tip, and at its base sending roots into the proto- 
plasm. I do not wish, however, to cast any doubts (however 
much I may feel them) on von Lendenfeld’s picture, as it was 
made from a sponge very far removed from Leucosolenia. 
I never observed any continuation of the flagellum into the 
interior of the cell. As to cell-contents, I was unable to 
observe with certainty in the living condition the contractile 
vacuoles often described. Isaw a vacuole frequently, but could 
1 “ Studies on the Comparative Anatomy of Sponges:” iv, “‘ On the Flagel- 
lated Chambers and Ova of Halichondria panicea,” ‘Quart. Journ. 
Mier. Sci.,’ Jan., 1891. 
2 Biitschli, “ Protozoa” in Bronn’s ‘Thierreich,’ Bd. ii, Mastigophora, p. 673. 
