52 Nils Hj. Odhner. 
attached below the middle of the lateral side, are strongest and also 
shortest, as this part of the body side is concavely depressed (fig. 
84). This circumstance is of a great interest and may perhaps he 
explained as follows: — 
It seems as though the posterior part of the body, where the 
septal muscles are strongest, were more moveable than the preceding 
half; in both specimens the posterior end was also somewhat flexed 
towards below, whereas the anterior half was straight (fig. 75). 
This supposed greater movability may be due to the presence, at the 
posterior end, of the cloaca, where respiration takes place. The result 
of the stronger development of the septal musculature at this end 
is that by their contraction the median part of the lateral side, 
where the muscles are attached, yields to their contraction, so that 
a concavity or a shallow furrow arises on the surface at the line 
of muscle insertion. Such a yielding, however, can ensue only if the 
cuticula is thin and does not make an effective resistance to the 
traction of the muscles; thus it seems quite natural that we should 
find in Gymnomenia a lateral furrow which is not to be traced in other 
Solenogastres, where the cuticula is thick and strengthened by spicula. 
A similar primitivity as is exhibited by the muscular system 
is observable, from sections, in the nervous system. Not only are the 
nerve cords, the lateral as well as the pedal ones, situated immedi- 
ately inside the thin muscle sheath, thus nearer to the external 
surface than in other Solenogastres, but they are ganglious 
throughout, everywhere covered with a cell layer. A well defined 
cerebral centre is developed, which also exhibits an external co- 
vering of cells exactly similar to those of the nerve cords. From 
the cerebral centre, nerves covered with cells emerge to the upper, 
the lateral, and the under side of the body, the two last-mentioned 
connectives being separated from each other as in Proneomenia. — 
Between the lateral and pedal cords metameric commissures appear 
throughout the body. The position of the pedal nerve cords is 
entirely outside the strong septal mucles, though some fine fibres 
from the latter are inserted also outside the cords. The lateral 
nerves run slightly above the side furrows inside the feeble muscular 
layer, and are surrounded by the septal fibres. They are of about 
the same strength as the pedal ones. 
The genital glands contain both kinds of products. They are 
divided into secondary glandulae each connected to a dissepiment — 
— there are however a larger number of dissepiments than gonadial Å 
