CILIATION OF ECTODERM OF AMPHIBIAN EMBRYO. 477 
wall which contain blood-vessels and connective tissue. In the 
frog they are formed of the two layers of epiblast only. 
Clarke describes these organs, which he terms balancers, as 
being used to support the larva when it hatches and falls into 
the mud. This may be so, but they are certainly also used 
for the suspension of the larva from weeds. Their walls are 
not ciliated. 
Comparison of the Ciliation of the Frog and Newt. 
In both animals the anterior and dorsal regions are more 
richly ciliated than the ventral and posterior. 
In both animals the stomodzal pit and area immediately 
surrounding the stomodeum are especially rich in ciliated 
cells, which cause a strong flow of water into the stomodeum, 
where particles suspended in the water may be seen whirling 
in eddies for a time and then passing out over the posterior lip. 
In both animals a very distinct stream of water is produced, 
which passes first over the olfactory epithelium, and subse- 
quently washes rapidly over the developing external gills. 
In the newt this stream appears to be the main flood, into 
which tributary currents flow from both the dorsal and ventral 
regious (vide figs. 21 and 22). 
In the frog this stream is in the main parallel with other 
currents, but is distinguishable by its very much greater 
rapidity (vide figs. 12 and 14). 
In the frog currents are set up by the ciliary action at an 
earlier stage, and are maintained to a later stage than in the 
newt. In the newt the tail soon loses its ciliation, whereas in 
the frog it remains active almost up to the time of the meta- 
morphosis. 
If a ciliated ectoderm really is ‘ evidence of a very archaic 
organisation,” a consideration of the exact distribution of the 
cilia, and the determination of any special areas or bands of 
cilia at the several stages of development of the embryo, may 
be of great morphological interest. 
Although I am inclined to think that at no time is every 
VOL. 388, PART 4—NEW SER. KK 
