CILIATION OF ECTODERM OF AMPHIBIAN EMBRYO. 467 
the cilia working from head to tail, causing the animal when 
perfectly quiet to move forwards slowly in the water.” 
Preyer (12) and Carriere (2) also describe the presence of 
cilia upon the external gills of Salamander and Siredon re- 
' spectively. 
Stohr (15), in a very brief account of the “sogen Haft- 
organe” of the Anura, describes the action of the cilia in 
connection with these organs, to which I must refer again. 
The ciliated ectoderm of Rana temporaria. 
The first signs of the presence of cilia in the frog embryo 
occur shortly before the closure of the neural folds. At the 
time when the folds are first visible, and even when they are 
commencing to fold, there is still no trace of ciliation. 
Fig. 1, Pl. 85, represents the earliest stage at which I have 
detected any ciliary movement. I have not at this stage seen 
the cilia, but have observed a streaming of carmine granules 
along certain regions. 
It will be seen that the edges of the neural plate are raised 
up as prominent ridges, but as yet they have not met at any 
point. The anterior or cranial portion is marked by its great 
lateral expansions, which do not become infolded, and which 
give rise to the ganglia of certain of the cranial nerves. It is 
upon these lateral expansions and the actual edges of the 
neural plate that the cilia are first developed. The arrows in 
fig. 1 indicate the direction of flow of the current set up by 
the action of the cilia upon the surrounding fluids. 
Fig. 2 shows the extent and course of the current when seen 
from the side a few hours later. The neural folds have not as 
yet met. 
As the neural folds bend upwards the current becomes more 
marked and extends somewhat further back, and also rather 
further ventral-wards. 
Just before the neural folds close—when they have closed 
anteriorly, but are sufficiently open along the back to allow a 
view of the neural groove—a distinct motion is visible upon the 
anterior ventral surface of the embryo,—that is, over the area 
