CILIATION OF ECTODERM OF AMPHIBIAN EMBRYO. 475 
There are no. cilia upon the extreme dorsal and ventral edges 
of the tail. There are none on the eyes. 
The motion of water over the body becomes slower, and in 
a 20-mm. tadpole it can hardly be termed a flow. The ciliated 
cells are now so few and far apart, and so feeble, that a series 
of eddies takes the place of a regular streaming. This, how- 
ever, is not the case with the tail. Scattered all over the sides 
of the tail are cells which in surface view appear elongated 
(fig. 18, C.), and bear long and very active cilia, which work in 
the direction of the shortest axis of the cell. 
The general result of the action of these cells is the produc- 
tion of a rapid flow of water from about the level of the noto- 
chord in a diagonal direction, both dorsally and ventrally. A 
granule of carmine may be seen to be dashed from one cell to 
another like a shuttlecock, and made to take a zigzag course 
across the tail fins, as indicated in fig. 17. 
As the tail expands these cells become more and more sepa- 
rated, and so become less numerous to a given area where the 
tail expands most, and remain more numerous towards the 
base (fig. 17). 
Fig. 18 is a camera drawing of the surface of the tail of a 
tadpole 19 mm., showing the ciliated cells, which are at this 
stage more deeply pigmented than the majority of the other 
surface cells. On the development of the hind limbs and 
diminution of the tail the cilia disappear from the tail, as from 
the rest of the epidermis. 
The Newt (Triton cristatus). 
I have not observed any cilia or currents of water presum- 
ably due to cilia before the complete closure of the neural folds 
in Triton cristatus. Ido not, however, wish to assert that 
there is never any ciliation prior to that time, as my observa- 
tions have been few in number. Clarke (8), as quoted above, 
also seems not to have noticed the cilia until after the closure 
of the neural folds. As the head and tail become distinct the 
whole of the anterior end of the embryo is richly ciliated, and 
