The Morphology of a Solenogastre. 707 
pharynx become abruptly thicker and on each side of the mid line 
are developed into a prominent diverticulum (Fig. 4, s. g). In 
addition to the slender supporting cells with centrally placed nuclei 
there are large numbers of gland cells each with a basal nucleus and 
an abundance of a glandular secretion. In the later stages the 
granules become confluent and pass out through minute pores in the 
overlying cuticle. In position and probably in function these organs 
correspond to the dorsal salivary glands of other solenogastres. 
The radula and its attendant muscles are enormously developed 
and indicate active predatory habits but further evidence concerning 
the nature of the food is lacking for in all the specimens the stomach 
is practically empty and the contents of the intestine is merely 
diatoms, sponge spicules and inorganic debris. As Fig. 14 shows 
the radula is of the distichous type and contains 28 transverse rows. 
Each tooth is accurately represented in Figs. 12, 14. There is no 
visible suture between the inner smaller projection and the outer 
horn-like cusp, which are therefore to be considered parts of a 
single tooth. 
As may be seen in Fig. 17 a basement membrane is present, 
clearly visible between the teeth but elsewhere so closely fused 
with their bases as to be almost invisible. In the early stages of 
their development and during their passage down the radula sac 
the two rows are in close contact and the basement membrane is 
continuous across the mid line; but at the point of entry into the 
pharyngeal cavity a cleft appears between the radular supports 
(Fig. 11) into which the epithelium supporting the basement membrane 
projects. It will be seen that the two rows continue to remain in 
close proximity to each other but in reality are separated by a 
wide extent. Under such circumstances the basement membrane 
splits along the mid line, a half remaining with each row of teeth. 
This peculiar condition of affairs is a device to allow the opening 
and closing of the teeth in the act of collecting food (see page 714). 
As HeuscHER (1892) remarks the relations of the various groups 
of cells at the posterior end of the radula sac are strikingly similar to 
those of the prosobranchs and chitons figured by Rösster (1885) and in 
the present species the resemblance is even more close than is described 
for Pr. sluiteri. The odontoblasts form two conspicuous groups on 
either side of the mid line and are composed of not less than 100 
cells each. They are of the usual high and slender type and are 
finely granular with the exception of the cytoplasm adjoining the 
