56 
(Lc. -p. 599) the “collar-cavities” of Amphioxus and thus 
homologized to the homonymous cavities of Balanoglossus. 
The other mesodermic segments, according to him, are 
all separated from in front backwards from a pair of, 
„coelomic grooves” which after their separation from the 
entoderm communicate with the gut only at their posterior 
er.d. They are compared with the trunk coelom of 
Balanoglossus. 
VAN WYHE (1902, p. 176) joins MACBRIDE in his deri- 
vation of the metamerism of Amphioxus from an original 
trimerism as in Balanoglossus and Fchinoderm-larvae and 
tries to extend the comparison also to Craniates. Protocoel, 
mesocoel and metacoel, proto-, meso- and metasoma accord- 
ing to this conception may be distinguished in Chordates 
as well as in Balanoglossus and other deuterostomian 
“Prochordates”. The opening of HATSCHEK's pit is compared 
by BATESON (1885) with the proboscis-pore of Balanoglosstis 
and the water-pore of Echinoderms. GOODRICH (1917) tries 
to extend this comparison to the so-called premandibular 
somites of Craniata. He claims that in Selachii these acquire 
an opening into the hypophysis which he homologizes with 
the preoral pit of Amphioxus. In this direction then the 
connection of the Chordates with Evertebrates has been 
sought in recent times. 
From the point of view of my theory, however, these 
recent attempts to solve the old question cannot lead to 
any good. In my opinion the metamerism of Vertebrates 
has been directly inherited from the Annelids and has nothing 
to do with the trimerism of the so-called “Hemi- and Diplo- 
chordates” of BATESON and MASTERMAN. Truly, in the 
Annelid body also, we can, if we wish, distinguish three 
regions, the prostomium, the peristomium and the rest of 
the segmented body. The situation of the mouth agrees with 
that of Balanoglossus in that it lies in front of the peristomium 
and the collar respectively. Whether a deeper significance IS 
to be attributed to this agreement (cf. SPENGEL, 1893) is 
a question as obscure as that of the relation of Proto- and 
Deuterostomia to one another. Probably, however, they have 
nothing to do with each other. 
Brain vesicle of Amphioxus — Another question raised by 
the comparison of the anterior end of the body in Acrania 
and Craniata is that of the relation of the brain vesicle of 
the former to the brain of the latter. Several attempts have 
