706 Harorn Hears, 
epithelial lining consists of small cubical cells and is developed into 
a number of pronounced longitudinal folds covered with a heavy 
cuticle which acts as a protection against the great teeth of the 
radula. The limits of the pharynx are not sharply defined yet 
judging from other molluscs it may be said to include the wide 
space into which the tongue projects and the dorsal salivary glands 
open. Behind this last named region the oesophagus arises as a 
slender tube and passes backward into the stomach. 
The walls of the subradular part of the pharynx have been 
shown to to be modified in two species of solenogastres (HEATH, 1904) 
into sense organs which, judging from their structure and nerve 
supply, are doubtless the homolog of the subradular organ in the 
chitons and certain prosobranchs. In the present species this structure 
exists yet not with the characteristic sharpness of the chitons nor 
of Proneomenia hawaïensis. The cells form a single group in the 
mid line (Fig. 4 s. r. 0.) and possess a considerable degree of glandular 
activity, yet judging from their special nerve connections originating 
in the labio-buccal system (Fig. 7, s. c.) we must look upon this as 
a true subradular organ. The component cells shade rather abruptly 
from the low cubical elements of the‘ pharynx in general into the 
high columnar cells of the group in question and as noted are more 
or less glandular. 
Hauer (1883) described gland cells in the subradular organ of 
Chiton siculus but their presence has been denied by others. However 
in certain species of chitons that I have examined, notably Trachy- 
dermon raymondi, glandular products undoubtedly exist in many of 
the subradular cells. On the other hand I have not recognized them 
in several other species of chitons nor in Proneomenia hawatiensis 
so it appears that there is considerable variation in this respect in 
the amphineura. The same holds true for the subradular organ 
itself. As just remarked it is prominently developed in the chitons 
and in Proneomenia hawaïiensis (and apparently in Pr. sluiteri). On 
the other hand no trace of it nor of its nerve supply has been found 
in the genus Chaetoderma. In Rhopalomenia scandens the subradular 
ganglia are not well defined and the organ itself is not clearly 
differentiated. From such scant data we seem to be justified in the 
belief that in the solenogastres this organ tends to disappear as the 
radula vanishes. 
At a point corresponding closely to the forward end of the 
radula in Fig. 3 the cells of the dorsal and lateral walls of the 
