Norwegian Solenogastres. 69 
Mollusken erblicken wir Spuren einer sehr bemerkenswerten Uber- 
einstimmung zwischen diesem Thierkreise und den Anneliden.« This 
statement is quite justified, but should not be understood to imply 
a direct origin of the former from the latter. The agreement is in- 
volved in the fact that the coelomoducts »den Character von Seg- 
mentalorganen haben und urspriinglich zugleich als Ausfiihrungs- 
gange der Geschlechtsorgane und als Nephridien fungiert haben«. 
On the one hand we can establish this similar organization, 
on the other a very different segmentation. In comparing the gono- 
pericardial tubes of the Solenogastres with the coelom of the Anne- 
lids we find that the former is continuous, and in view of this fact 
the question arises whether this is a primitive or a secondary cha- 
racter, and whether the presence of a single pair of »segmental 
organs« is primitive or secondary; briefly: how is this single pair 
of »segmental organs« to be explained? 
It may be asked whether this single pair has developed from 
the hindmost one of the Annelids in connection with a suppression 
of the preceding ones at the same time as the coelom sacs secondarily 
break up into a continuous canal; or whether, on the contrary, tite 
conditions prevailing in the Solenogastres are primitive, and those 
of the Annelids secondarily acquired. Also a third possibility is 
conceivable, viz. whether the whole body of a Solenogastre is to be 
considered homologous with a single segment of an Annelid. Such a 
comparison is of course untenable and is disproved by the segmen- 
tation of the intestine and the nervous system. The first alternative 
must also be dismissed for the reason that the unsegmented habitus 
is, of course, primitive in relation to the segmented, whence an in- 
verse origin is very improbable; and lastly, the second alternative 
is improbable, seeing that the segmentation of the Solenogastres and 
the Annelids is of a different kind, the former ones having their 
dissepiments on opposite sides sometimes alternating and developed 
in series of increasing size like the septa of Anthozoa. Further no 
correspondence exists in the metameric structure of the different 
organs. 
The difficulties which arise when we endeavour to explain the 
presumed homology of the coelomoducts and the segmental organs 
seem insurmountable, and this forces us to attempt to attack the pro- 
blem from another side. LA 
Instead of comparing the segmentation with that of an Annelid 
we may find closer conformity with that of a Nemertine; but seeing 
