Hector F. E. Jungersen: Chordeuma obesum, a new Parasitic Copepod. 9 



an extremely narrow space, The stomach (in) is a capacious, pear-shaped sac, tapering 

 backward and ending blindly in the last thoracic segment; it has a single layer 

 of rather flat epithelial cells. It always contains an ovoid body, concentrically 

 composed of layers, probably indigestible matters deposited as a kind of "stone", as 

 there is no practicable way to get rid of any faeces. In some cases this "stone" may 

 be large enough to be seen with the naked eye. 



Nervous System. (Fig. 8). The brain (eb) is situated dorsally to the antennæ, 

 close in front of the oesophagus; it is rounded and provided with a coating of ganglionic 

 cells; a short, rather broad commissure on each side of the oesophagus connects 

 with the ventral nerve-mass (nv.); the structure of the latter is the same as that of 

 the brain; it lies dorsally to the maxillæ and tapers into a thread coated with nerve- 

 cells and reaching at least through the first and second thoracic segments. From 

 each side of the brain a long nerve is seen going to the antennules; from the broad 

 anterior part of the ventral mass other nerves are going to the maxillæ, but the 

 greater part of the peripheral nerves I have not been able to make out. 



Muscles. (Fig. 8). The muscles of the body form quite narrow ribbons, isolated 

 from each other by considerable interspaces. The longitudinal muscles are made up of 

 four dorsal and two ventral ribbons. The former — one pair of dorsal (md), and 

 one of latero-dorsal (mdl) muscles — take their origin from the inner concave surface 

 of the head in the region of the ovary and stop at the last thoracic segment, being 

 divided for each segment by an insertion in its front margin. The latero-dorsal 

 pair are a little stronger than the dorsal. The ventral pair (mv) take their origin 

 inside the head near the middle of the base of the maxillæ; from here they diverge 

 feebly in the head and first thoracic segment, are almost parallel in the second and 

 converge evenly through the third and fourth, almost meeting at the same point of 

 insertion in the front margin of the genital segment. Thus the abdomen has no 

 longitudinal muscles of its own but is acted upon by means of those of the trunk, 

 the flexors acting directly, the extensors indirectly. 



There are several pairs of transverse and oblique muscles originating dorsally or 

 dorso-laterally in the head and thorax and inserted at the base of the appendages; 

 some of thera seem to be fastened rather to the body-wall near the limbs than 

 directly into the latter, and it is not quite clear to me, hnw they may aet on the 

 appendages. Most of these muscles brlong to the head and first thoracic segment, 

 and here they run obliquely in difTerent directions (cf. Fig. 8), some of them more 

 superflcially than others and therefore more easiiy seen. In each of the three last 

 thoracic segments only one pair of strictly transverse muscles is found, running 

 deeply on each side, between the stomach and the oviduct. 



In the abdomen a set of deep strong muscles is observed, the paire<i nature of 



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