78 Nils Hj. Odhner. 
analysed and homologised, which undoubtedly would be of a great 
systematical importance and of great value for taxonomy. With a 
view to emphasizing this essential importance of the coelom for- 
mation, it may be convenient to give a brief resumé of the charac- 
ters of the Solenogastres in the following definition: 
They are uncompletely segmented or un- 
segmented Scolecids without special protone- 
phridia, with a continuous tubiform gonocar- 
docoel, a differently developed combined hae- 
molymphocoel with a localized contractile 
heart, cloacal respiration.and a cuticularized 
body surface. 
Chaetodermatina differ widely from Neomeniina; only to the 
latter is the name Solenogastres adapted. This name, however, 
was given by GEGENBAUR (1878) to comprise both sections. More 
expressive inclusive ames would be »Telobranchiata« as pro- 
posed by Koren & DANIELSSEN in 1877, and »Scolecomorpha<, used . 
by LANKESTER, in the same year, but both these names refer to the 
Neomeniina only. Though an exchange of the group names 
would render them more apposite, this is disallowed by the rules 
of nomenclature. 
From the Solenogastres the Mollusca are essentially distinct 
(though most probably derived from a Common root). Their higher 
organization is manifested by the presence of a differentiated foot 
and a mantle and, typically, a subpallial cavity containing respira- 
tory organs in the form of ctenidia. 
The opinion set forth here as to the affinities of the Soleno- 
gastres is in opposition to the hypothesis established by PELSENEER 
that the Mollusca (inclusive of Solenogastres) are probably to be 
derived from Annelids, and agrees with the older opinion repre- 
sented by those authors who, like LANG, THIELE, PLATE, NIERSTRASZ, 
SIMROTH and others, suppose that their origin is to be sought for 
in the Plathelminthes. In this respect there is entire accordance 
with the view of THIELE (1902), who moreover considers the So- 
lenogastres as worms and no molluscs. Further, it may be remarked 
that the explanation given above as to the phylogeny of the deutero- 
coel in Solenogastres and Mollusca speaks in favour of the gono- 
coel theory, and that the opinion regarding the haemo-lymphocoel 
clashes with the haemocoel theory by LANG (1903), who endeavours 
to derive the heart and the blood vessels of i. a. Mollusca from the 
