Norwegian Solenogastres. 17 
from the posteriorly placed radula sac. In Simrothiella, on the 
other hand, such a process is rendered impossible by the pre- 
sence of a formative region in each end of the radula. The 
latter must have a fixed position and be secreted as a cuticular 
covering of the matrix cells precisely in the manner assumed by 
Wiren to be the rule among the Solenogastres (cf. Wirén 1892 
p. 84). In reality the teeth of the present species are all (except 
the foremost adult ones) entirely embedded in the epithelium the 
cells of which are everywhere of secretory function and serve as 
odontoblasts, strengthening the teeth by gradual apposition of 
new gelatinous substance. Teeth of this type of radula, as a 
matter of fact, are bound to increase in number with age. Their 
number as well as the number of rows in the radula of a So- 
jenogastre, thus seems to be subject to variation according to 
the size of the animal. 
The radula of Simrothiella, thus exhibits a highly specialized 
construction. It is improbable that such a specialization has 
arisen after a reduction from a higher type of radula, as in the 
case of Gastropoda. The contrary is much more likely, namely 
that it represents a peculiar differentiation of the cuticular stage, 
and that this stage is primitive in the present case as well as, 
most probably, in all the Solenogastres. 
Simrothielia thus seems to support the view that the Soleno- 
gastres, as regards their radula are primitive organisms subjected 
to a progressive development: the forms in which the radula 
shows the best conformity with that of the Gastropoda represent 
an advanced progressive stage in relation to the remaining ones 
which may be regarded as primitive. This question will be 
further dealt with in the sequel. 
With regard to the alimentary canal of Simrothiella, a few 
anatomical details may be added to those already mentioned. 
The ventral salivary glands (fig. 1, v.s.g.) debouch into the oes- 
ophagus; they are shorter than the posterior part of the radula 
sac and embedded in its dorsal wall. A small dorsal salivary 
gland (d.s.g.) is present just in front of the oesophagus. The 
whole pharynx is attached by means of a few muscle cords (m) 
to the body wall. 
The intestine has a slight trace ‘ai a dorsal coecum and is 
throughout its whole length divided into diverticula, which, how- 
ever, are only slightly developed and separated merely by very 
