SUMMARY 479 



SUMMARY 



It is suggested from a comparison of the limb arrangement of Doloria with that of a 

 Cyprid, that the principle of feeding is the same in Cypridinids as in Cyprids, but that the 

 limbs which carry out the various processes involved in the feeding mechanism are not in 

 all cases homologous. Thus a food stream through the shell is produced by the vibratory 

 plate of the maxillule in the case of a Cyprid and of the maxilla in a Cypridinid. 



The skeletal stability of the body of Doloria centres on the powerful adductor muscle 

 which connects the two valves. The limbs are connected to a massive endosternite, 

 which forms the tendon between the right and left halves of this muscle, by a series 

 of strong apodemes. In addition to this endoskeleton, the limbs and paired eyes are 

 supported by a system of articulating sclerites which radiate from the attachment of 

 the adductor muscle to the valves. 



The dorsal body wall forms a soft flexible dome between heart and caudal furca. 

 It is peculiar in that its musculature consists of a chequer-work of muscles, formed 

 of the dorsal longitudinal muscles and a series of circular muscles lying close inside 

 the ectoderm, both sets of muscles being connected to the cuticle. It is suggested that 

 the latter are of ectodermal origin. 



The globular heart, which possesses one pair of dorsal ostia, is slung on a muscular 

 pericardial floor. Its walls fuse with the latter in three places, where splits occur which 

 are bounded by myofibrils and which act as valves from the heart. A pair of these lead 

 directly into a system of ramifying channels in a parenchymatous tissue which surrounds 

 the gut. The third opens into an aorta. 



The aorta leads into a circular vessel surrounding the oesophagus which opens into 

 the body cavity underneath the endosternite. In addition, it gives off antennal arteries 

 which can be traced to their termination in the protoplasm of the powerful swimming 

 muscles in the bases of the antennae. 



The whole system of blood vessels is provided with a series of muscles running in 

 their walls (not circular muscles), or attached to their walls by which they can be dis- 

 tended or collapsed. In addition, there is a pair of muscular valves at the point where 

 the main vessels open into the body cavity. It is suggested that this muscular system 

 is an accessory circulatory mechanism, and, from a study of the arrangement of the 

 muscles, it has been possible to suggest the actual mechanism by which the blood is 

 forced round the body. The heart does not appear to be essential, and this is significant 

 from the fact that in many Ostracods the heart is absent. 



The gut musculature consists of a chequer-work of fibres which appear to be homo- 

 geneous, showing no trace of striation. 



The compact nervous system is peculiar in that a basal ganglion occurs in each limb. 

 A well-defined system of giant fibres is present, most of which are, as usual, associative 

 elements, but some are apparently motor neurones which can be followed to their 

 temiination in the large muscles of the antennae. A well-defined sympathetic system 

 is present, and shows a marked similarity to that of Astacus. 



