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behind the auditory capsule only, the latter being considered 
by HATSCHEK as belonging to the unsegmented anterior end 
of the Annelid, distinguished by him asthe head (cf. anon). 
KLEINENBERG (1886, p. 190) has shown the inadequacy of 
HATSCHEK's definition of the head and has replaced it by 
another by which this term was restricted to the prostomium 
and the statocysts were counted to the segmented soma. 
Yet the suggestion made here by HATSCHEK agrees closely 
with the second fundamental idea of my theory which at 
first sight might appear so hazardous thas 1 was glad to 
find a predecessor like HATSCHEK. 
Brain of Annelids and Craniates. — A question which now 
presents itself is, whether it might be possible to trace back 
the foundations upon which in the course of phylogeny 
the complicated brain of higher Craniates has built itself 
up to certain structures of the apical plate of Annelids. The 
cerebral ganglion or brain of Annelids does not represent 
a simple structure but is composed of several centres, 
each having a separate function and origin. According to 
HATSCHEK (1891, p. 424) and RACOVITZA (1896) we may 
distinguish in the prostomium from in front backward: 
1. an anterior pair of “Tentacularganglien” or “cerveau 
antérieur,” innervating the so-called primary tentacles or 
palps which originate at bcth sides of the larval apical 
sense organ at the animal pole, 
2. a “Mittelhirn” or “cerveau moyen,” innervating the. 
eyes and the antennae, 
. a pair of “Riechlappen” or “cerveau postérieur” inner 
vating the ciliated pits. 
Each of these three centres owes its origin phylogenetically 
and ontogenetically to a sense-organ of the praeoral lobe; the 
nervous centre is produced by the sense-organ innervated 
by it, as stated by KLEINENBERG (1886). Three sensitivo- 
nervous regions then may be distinguished in the cephalic 
lobe: “la région palpaire est gustative et tactile, la région 
sincipitale est tactile et visuelle, la région nucale est olfactive”. 
ften the ganglia in Annelids remain in direct contact and 
are connected to the part of the epidermis from which they 
have originated and with the sense-organs to which they 
belong. Often, however, part of the ganglion detaches itself and 
now lies in the interior of the praeoral lobe, connected by 
a short nerve with the other part which remains applied 
to the sense-organ. In this way three centres ofthe Annelid 
