GUT 46s 



a zone where this layer is thickened and extends inwards to the inner epitheUum, and 

 here the cells have a similar shape. 



The gut parenchyma is produced postero-dorsally in a series of five ridges, which 

 extend up and attach to the body wall in between the dorsal longitudinal muscles. In 

 this way the body cavity is divided up into a series of aisles. Each ridge consists of a 

 plate of reserve cells covered by a very attenuated layer of the outer epithelium. 



Laterally the parenchyma sends an outgrowth on either side, which extends a short 

 distance into the valves. 



Anteriorly the gut parenchyma sends outgrov^ths towards the pericardium, along the 

 aorta and to the antennal glands in the basal joints of the antennae. 



The aortic outgrowths lie close against the aorta, and extend to the anterior limit 

 where the latter ends blindly. The pericardial outgrowths extend up to the hepatic 

 valves (Fig. 11), and along their length there is a well-defined channel connecting the 

 heart directly with the canalicular system of the parenchyma. 



The antennal outgrowths extend into the base of the antenna and surround the duct 

 of the antennal gland and the basal ganglion of the antenna. They difi^er in constitution 

 from the rest. They contain no reserve cells, or, if they do, they contain no coagulable 

 staining matter. They consist simply of large polyhedral cells which stain very faintly 

 and resemble the cells which have already been mentioned as surrounding the heart. 



NERVOUS SYSTEM 



The anatomy of the nervous system of Ostracods and more particularly of Cypridinids 

 is very incompletely known. Miiller (1894, PI. 40, fig. 10) published a figure showing 

 the general structure of the nervous system oi Pyrocypris punctata, but did not describe 

 it in any detail, and it is on this figure that Klie, in a recent paper (1929, p. 39), bases 

 his general account. The most complete description of any Ostracod nervous system 

 is that of Gigantocypris published by Liiders (1909), but he had very little material 

 and apparently was unable to cut many sections. 



Recently Hanstrom has published several accounts (1924, 1927 and 1928), basing 

 his observ^ations on Eucypris fnscata and Philomedes globosa, but he deals chiefly with 

 the internal arrangement of the nerve centres and fibre tracts. Apparently, however 

 (1927, p. 240), he experienced great difficulty in fixation, and has not yet obtained a 

 series of sections from which he can describe the finer histological detail. 



Claus (1891) described in fair detail the anatomy of the Halocyprid nervous system, 

 and includes a figure of a section of the brain of Cypridina mediterranea. 



EXTERNAL ANATOMY 



The present description is based on a wax model, reconstructed from a series of 

 sections frontal to the nerve ring. 



The shape of the central nervous system can be seen from Figs. 9 and 10. It consists 

 of a massive circum-oesophageal ring to which is attached posteriorly, by a pair of 

 short stalks, all that remains of the ventral chain of ganglia. 



