CILIATION OF ECTODERM OF AMPHIBIAN EMBRYO. 471 
und ihr Klebriges Sekret in einem Hohlraum ergiessen, aus 
welchem dasselbe durch Flimmerharre nach Aussen befordert 
wird.” 
Fig. 8 is a semi-diagrammatic section across these organs of 
a tadpole of Rana temporaria 8 mm. long, at which time 
they reach their greatest development. 
They are essentially of the nature of mucous glands, bor- 
dered by strongly ciliated ridges. 
They secrete a very sticky substance, by means of which the 
tadpole can anchor itself to any convenient object. The “pro- 
toplasmic processes” alluded to by Marshall and Bles are 
probably masses of exuded mucous or cement, and are thus the 
product of the cells rather than processes of the cells them- 
selves. 
Both the ciliated cells and the mucous cells are developed 
from the outer or epidermic layer of epiblast. The nervous 
layer of epiblast forms a single layer of cells as elsewhere. 
Fig. 9 is a semi-diagrammatic figure of a section taken 
rather further back than that represented in fig. 8. In this 
the ridges are more prominent. The long cement-secreting 
cells, C.C., really le with their bases much further forward 
than their necks and openings. 
Fig. 10 shows the ventral surface of a tadpole of 34 mm. 
The cement-secreting cells are in the depressions M. 
The sides of the ridges surrounding the glands are com- 
pletely covered with long cilia. 
The cilia here are the most conspicuous of all upon the body. 
These cause very violent currents of water, as indicated in 
the figure. The central current passes over the stomodzal 
depression (S) along the groove leading from the mouth be- 
tween the two glands. 
In an older stage, 64 mm., fig. 11, the glands have so in- 
creased in size as now to be practically joined across the mid- 
ventral line. This necessitates an alteration of the course of 
the central current, which is now thrown outwards, and is then 
caught by the strong lateral currents and passes round the 
