245 
may be asked if it is advisable or of any use to carry any 
further our speculations in this direction. Yet l will do so and 
will venture to draw some more conclusions which, whether 
they are confirmed or disproved in the fu'ure, in any case 
will have been of some use as a stimulus to further research. 
Lateral ganglia of Annelids homologous to spinal ganglia 
of Vertebrates? — In Annelids every lateral sense-organ is 
closely connected with a ganglion, the lateral gangiion, which 
envelops the elements of the ciiiated area like acap. These 
lateral ganglia are considered by EISIG (1887, p. 517) to 
be homologous to the parapodial ganglia of other Annelids, 
which ganglia, in agreement with this view, are absent in 
Capitellids and Polyophthalmids, which latter possess the- 
highest developed lateral organs. The development of the 
parapodial ganglia in Lopadorhynckus has been described and 
figured by KLEINENBERG (1886 p. 112). They originate as 
proliferations from the ectoderm, not far from but independent 
of the ventrat ganglia, and separated from the latter by 
the ventral muscle plate. Now KLEINENBERG (l.c. p. 220) 
had supposed that the spinal ganglia of Vertebrates cor- 
respond to the parapodial ganglia of Annelids, and this 
view is joined by EISIG (1887, p. 542). “Und auch die 
Frage, warum denn erstere Ganglien bei den Vertebraten. 
nicht mehr so wie diejenigen der Hirnnerven zu der Haut, 
respective den Seitenorganen ontogenetische Beziehungen 
aufweisen, lässt sich beantworten. Derselbe durch die Con- 
centrirung des Kopfes oder Gehirnes hervorgerufene Process, 
er an den übrigen Bestandtheilen des Seitenorgansyste- 
mes so tiefgreifende Veränderungen hervorrief, nämlich die 
Anbahnung einer einheitlichen und directen (Gehirn-) Leitung 
an Stelle der segmentalen, hat auch die ursprünglichen 
Hautbeziehungen der Seitenorganganglien (Spinalganglien) 
allmählich zum Schwinden gebracht” (lc. p. 543). 
The following, therefore, are, in concise ion the views 
formulated by EISIG: the original segmental communications 
of the lateral organs with the spinal ganglia, the latter being 
the homologues of the parapodial and lateral ganglia of 
Annelids, have been preserved only in the head; in the trunk, 
however, they have been lost and replaced by the collector. 
the ramus lateralis of the vagus. 
The views resulting from my theory, though agreeing on 
the whole with those of EISIG, yet make certain modifica- 
tions indispensable to bring the latter into agreement with 
