70 Nils Hj. Odhner. 
that the genital gland of the latter is divided into completely sepa- 
rated coeca, we must pass on to a still lower type in Order to find a 
condition comparable with that of the Solenogastres; such a con- 
dition we find only in a not or imperfectly segmented worm, for in- 
stance a Turbellarian. | 
The imperfect segmentation of the Solenogastres has a re- 
markable correspondence in that of the Turbellarians, which re- 
presents a similar stage of evolution, though in other respects the 
Solenogastres show a higher or otherwise differently specialized or- 
ganization. Above all, similarities between Solenogastres and Tur- 
bellarians are to be found in the intestine: Nematomenia with 
its simple alimentary canal corresponds to the Rhabdocoelian type, 
whereas the Dendrocoelian type is represented by those forms which 
have the intestinal diverticula best developed (Proneomenia, Dre- 
panomenia). ; 
Also the pharyngeal region, in view of its considerable vari- 
ation, shows conformity with the conditions prevailing in Turbel- 
larians, as pointed out by THIELE 1902, and in its simplest features 
it corresponds to the schemes represented by THIELE (1902, p. 411, 
figs. 16, 17), and by WILHELM! (1913 p. 54, fig. 31 B and D). 
The origin of a Solenogastre from the Turbellarian stage may be 
assumed to have proceeded as follows. The intestinal diverticula of 
the latter have been separated by the development of muscular septa 
in the interstices. The great dilatation of the intestine has caused 
the genital ducts to be placed on the dorsal side and in its median 
line, and the genital folliculi have been, concentrated to a series of 
large crowded hermaphrodite groups, in which the male organs 
occupy a lateral position and the female a median one, in agree- 
ment with many Plathelminthes. The concentration has suppressed 
the ducts from the folliculi, and the male ones open by internal 
ruptures, in some cases (Gymnomenia) appearing as canals. 
If we thus compare the continuous gonopericardial tubes of 
the Solenogastres with the genital apparatus of a Turbellarian, 
abstracted to a schematic simplicity, we must compare the coelomo- 
ducts with the efferent ducts of such a worm. 
The coelomoducts thus are originally parts of the genital appa- 
ratus and cannot be homologised with the so called »segmental 
organs« or nephridia of the Polychætes. These are namely, in a 
large number of forms, »in reality formed by the fusion of a true — 
nephridium with a genital funnel, two organs which in certain other 
