Norwegian ‘Solenogastres. TI 
and Nematomorpha as well as with the Archiannelids, it might 
be justified to assume that the Solenogastres have arisen from and 
are confined to a common original stock of the primitive worms 
on the one hand and of the Mollusca on the other. 
Worms realising such an original form are wholly unknown. 
Of those nowadays living, the Rhabdocoelid Turbellarians probably 
come it nearest. »The Rhabdocoelid Turbellariax, says BENHAM 
1901 (p. 12), »contain forms which approach more nearly than 
do any other of the orders to the ancestral Platyhelminth«. 
It would, however, be a failure to assume that the Solenogastres 
had originated from a typical Rhabdocoelid. One has rather to 
imagine the most primitive worms as a very variable assemblage of 
animals with potency of developing into different directions: now 
there existed a primary coelom, this be considered a primary or a 
secondary character, and from this group the Solenogastres, Nemer- 
tines and Nematods took their origin — now the coelom was sup- 
pressed in forms giving rise to the recent Turbellarians. 
In consideration of these diverse relations of the Solenogastres 
it may be justified to allot to them a corresponding position in ‘he 
zoological system and to place them, consequently, among the 
Scolecids as a. group coordinate with Plathelminthes, Nemathel- 
minthes and Nemertines. 
In assuming that the Solenogastres represent an ancient type 
related to a connecting link between the different trunks of the 
Scolecids we are able to explain the relations of these worms in a 
simpler manner than usually practised, namely from the basis of 
a progressive development instead of by means of the hypothesis 
of a degeneration, as is assumed for the orders of Turbellarians, 
as well as for the Nematods (cf. RAUTHER 1909). 
From the Annelids the Solenogastres differ in the fact that the 
former have cardo-, gono- and lymphocoel fused with each other 
and the haemocoel separated from this »coelom« as it is generally 
called; their nephridia are either distinct or fused with the coelo- 
moducts (but not with the coelom). 
In general we may say that numerous variations in the devel- 
 opment and various combinations of the special coeloms and organs 
representing them are to be found within the so-called worms, and 
that different groups of these animals are well characterized by 
respective combinations. The generally so called »coelom« is a 
feature of various origin, still far from having been thoroughly 
