729 Harozp HEATH, 
verwandte Gruppe von Würmern, welche durch die Beziehung, in 
welche der Uterus zum Herzen getreten ist, sowie durch Anfänge 
einer Radulabildung zu den Mollusken hinüberführen, unter denen 
die Chitoniden besonders durch die Erhaltung der Lateralstränge 
ihnen am nächsten stehen.“ 
In the following paragraphs it is not intended to attempt a 
discussion of all the objections raised by this and other authors 
but merely to try to show that some of them, of the most fundamental 
character, may bear a different interpretation. 
It is generally conceded that the typical members of the genus 
Chaetoderma, such as Ch. nitidulum, are the most highly modified 
species of solenogastres, the greatly reduced radula and the absence 
of a foot being the more apparent marks of a highly specialized 
condition. In other words a foot was present in the ancestral 
solenogastre and the radula was probably typically located and 
developed. Concerning the general shape of the body it is diffieult 
to speak. It now appears that as the foot diminished in size the 
mantle proportionately increased, finally covering the greater part 
of the animal but leaving the mantle cavity and its complex at the 
posterior end of the body. 
The foot, as we now know, contained two sets of glands 
designated by Husrecur (1881) the anterior and posterior pedal, 
the first named opening into the forward end of the mantle furrow 
the second accompanying the foot throughout its entire extent. In 
Limifossor all external traces of the foot have disappeared yet a 
space in the ventral somatic muscles, the overlying pedal sinus and 
perhaps a few gland cells in the anterior end of the body point to 
its former existence. 
Considerable difficulty has been encountered in the attempt to 
compare the pedal glands of the solenogastres with corresponding 
structures in the chitons. In the adults of the last named group 
the only true pedal gland is in the form of scattered pyriform cells 
which, in some species at least, are imbedded in the deeper tissues 
of the foot while the duct leads to an outlet between the epithelial 
cells. Neglecting the fact that the gland is diffuse it differs in no 
fundamental respect from the post-pedal gland of the solenogastres. 
In regard to the homologies of the anterior pedal gland the 
problem is by no means so easy of solution. Srrorx (1893) makes 
the remark that the so called larval pedal gland in young chitons 
„sehr an die vordere Flimmerhöhle (Fußdrüse) der Aplacophoren 
