144 Transactions of the Boyal Society of South Africa. 
The structure of the tubes must be described separately. Fig. V. 
shows two slightly oblique sections through the tubes of the raouth gland 
in the region underneath the first bunch of papillee ; a muscle fibre cell is 
seen running from the one to the other and the nuclei and plasma of 
other such cells are seen in cross-section surrounding the tubes. The 
tubes and muscle fibres are enveloped in an exceeding delicate sheath of 
connective tissue which is not seen in the drawing. The tubes them- 
selves are shut in by a single layer of cells and have somewhat irregular 
lumina. The cells are of a peculiar structure and must be compared with 
the muscular epithelia of Hydra ; the part of the cell towards the lumen is 
composed of clear protoplasm in which lies the nucleolated nucleus where- 
Fm. V. 
as the peripheral part is striated. It may, of course, be that the striae 
represent the secretion, but, as they are neither in the neighbourhood of 
the nucleus nor the lumen, this is not likely. It is probable that the striae 
are muscle fibrillae, stretched from centre to periphery, by means of which 
the tube may be compressed or dilated in order to force the secretion 
along the tube to the exterior. 
The tubes of the mouth glands of Spurilla are extremely muscular 
(Fig. III.). The Fig. represents the best section which I could find and 
is not good although I even went to the pains of dissecting out and pre- 
serving for themselves these glands. On the outside are seen two secre- 
tory cells, then comes a layer of neutral cells, then a thick layer of muscle 
fibres very sparsely nucleated (one longish, dark nucleus can be seen on 
the inner side in the Fig.) and lastly, another layer of neutral cells in 
