390 MR PATRICK GEDDES AND MR FRANK E. BEDDARD 
the lower part of the knob-like swelling at the extremity of the calcareous rod 
of the stalk, and, as in the case of the other muscles in the different pedicel- 
lariz, there is no appearance of anything comparable to tendinous tissue. 
Those fibres present a very great contrast to the stalk fibres in the other 
pedicellariz, being of a uniform diameter, with a sharp outline, and resembling 
very closely the transverse muscles of the head of this and the other kinds of 
pedicellariz. 
Plate XXL, fig. 6, shows the upper extremity of the rod with the stalk fibres 
attached to its lower portion. Fig. 7 is the same structure, but, viewed from 
above, the stalk fibres are attached all round, and radiate outwards from the 
calcareous rod. Fig. 8 is a section through the stem of a gemmiform pedicel- 
laria, broken somewhere below the distal knob-like extremity ; the rod itself is 
seen to be made up, as described above, of a number of delicate longitudinal bars 
connected by transverse pieces; outside the calcareous rod is the epithelial coating. 
The structure of the head itself is very peculiar. When the three valves are 
closed, it is almost globular in shape. Each of the three calcareous valves 
(Pl. XXI. fig. 1) consists of a basal portion of a squarish shape with rounded 
angles ; at the sides are tooth-like prolongations for articulation with the other 
valves ; the upper part of the valve is prolonged into a slender hollow rod, 
triangular in section, and provided at its extremity with a sharp process at 
right angles to itself. The lower portion of the valve is provided with an 
apophysis for the attachment of the approximator muscles. Each of the three 
valves has attached to its outer surface a large glandular mass, which in the 
intact pedicellariz almost entirely conceals the underlying calcareous parts. 
We have studied these pedicellariz, as well as the others, both by teasing and 
by sections, but the latter method gives very good results in this case, because 
of the great development of soft parts which renders the cutting of sections far 
easier than in the other pedicellariz, where complete sections cannot well be 
obtained, owing to the predominance of the calcareous skeleton of the “head” 
over the soft parts. Underneath the epithelium lie the three glandular bodies, 
the structure and relations of which will be best understood by describing in 
order the three sections given on Plate XXI._ Fig. 10 is drawn from a section 
through the lower part of the head. Each of the glandular masses is somewhat 
kidney-shaped in section, and is attached to the outer surface of the calcareous 
valve of its own side. The centre is filled with a mass of glandular and some- 
what elongated cells, outside which is a double layer of fine muscular fibres, 
unstriated, which cross each other nearly at right angles, and in a direction 
oblique to the long axis of gland. They no doubt serve to compress the gland 
and squeeze out the secretion. Surrounding the whole is seen the epithelium, 
which is thickened in a peculiar manner at the lower corners of each of the 
glandular masses. Connecting the apophysis of the calcareous valves are the 
